Here’s my translation

Alan

Þeir sögðu þessa sök búna vera á hendr Markúsi um sauðaskurð á mót þeiri sök, er hann hafði á höndum Inga um bænahústoll. 
They  said this charge to [have] be[en] prepared (ie ‘fixed‘, fem acc sg strong of  pp of <búa>, cf búa mál á hendr e-m, Z1) against Markús about [the] sheep-slaughter in-exchange-for that charge, which he (ie Markús) brought (lit: had, <hafa> Z6) against Ingi about [the] house-of-prayer (chapel)-toll.

Ok síðan drógu þeir glott at ok mikit skaup, at Markús mundi eigi allt réttiliga fá til bús síns, ok höfðu mörg heimslig orð um þetta mál.
And after-that they drew sneers at [them] and great mockery (ie they sneered at and greatly mocked them), that Markús would not altogether justly lay-hold (<fá til e-s>, Z12 ?) of his-own farm, and [they] used (<hafa>, Z4) many foolish words concerning this matter.

Nú við þessi slög þeira ok illt orðalag þá reiddist Markús mjök ok kvaðst eigi lengi mundu nenna at sitja sér minnum mönnum slíkan ósóma, er þeir tóku upp.
Now at these skirmishes and ill manner-of-speaking, then Markús became-very-angry (cf <verða reiðr við e-t>, under <við>, Z7) and declared-of-himself [that he] would not long be inclined to endure (<sitja e-t>, Z6) such dishonour (<úsomi>) to his lesser folk (men, ie his underlings, manservants), which they took up (If <þeir> refers to his manservants <which they put up with, endured>; if it refers to their abusers, then <which they raised, adopted against (his manservants)?)

7. Víg Markúss ok eftirmál.
7. [The] Slaying of Markús and action-against-the slayer-on-behalf-of-the-slain.

Þá er þessi mál hófust, þá dreymdi þann mann draum, er Guðbrandr hét Gestsson. 
When these affairs began (arose, hefjast) then a dream was-dreamt by that person (man) who was-called Guðbrandr Gestr’s-son.

Hann dreymdi þat, at honum þótti maðr koma at sér, mikill ok svartr ok illiligr. 
That was-dreamed by him, that [it] seemed to him a person (man) came upon him, tall and black (or baneful) and hideous.

Hann þóttist spyrja, hvat manna hann í væri. 
He bethought himself to ask, what [race] of persons (men) he was in (ie belonged to).

Sá svaraði ok kvað vísu:
That-one (ie He) answered and recited a verse:

Version A:
(see under Version B)

     Líðr gótt sumar gróðrar.

     Gandrekr þrumir. Landa

     heimr es með beztum blóma

     birtr. Nú es ráð at hirtask.

     Mjök es grimmliga glýjaðr,

     gapir hann á sjöt manna

     olmr und ægishjálmi,

     Ingólfr kominn hingat.


Version B


Líðr gróðrar gótt sumar. 
A good summer of growth (gen sg) passes.

Gandrekr þrumir. 
A gale-brought-about-by-witchcraft (<gandrekr>) persists (sits fast).

Landa heimr es birtr með beztum blóma. 
[The] region of lands (as distinct from the seas) is (<es> = <er>) illuminated (pp) with the best bloom (blossom, dat masc sg of <blómi>)

Nú es ráð at hirtask. 
Now [it] is a good-idea (lit a plan) to chastise one’s-self.

Ingolfr es kominn hingat, mjök grimmiliga glýjaðr. 
Ingólfr is (<es> = <er>) come hither, very fiercely gleeful.

Hann gapir olmr und ægishjalmi á sjöt manna:
He gapes furious under [the] helmet-of-terror (<oegishjálmr>, not to be confused with the helmet of Ægir the giant) on [the] abode of people (men, mankind) (ie = Earth)

Version C:


Hið gróðursæla sumar er liðið. 
That growth-blessed summer is (has) passed.

Stormur blæs í sífellu. 
A gale blows constantly.

Jörðin ber hinn blómlegasta ávöxt. 
The-earth bears the most-blooming growth.

Nú er ráð að hirta sjálfan sig. 
Now [it] is a good-idea  to chastise one’s-self.

Ingólfur er kominn hingað grimmdarglaður. 
Ingólf is come hither fiercely-cheerful.

Hann starir ólmur með agishjálm á heimkynni manna.
He gazes wild with [the] helmet-of-terror on [the] abode od people (men, mankind)

Þann draum hyggjum vér verit hafa fyrir þeim ófriði, er á Rauðasandi varð.
We believe that dream to have been for (ie to represent) that hostility, which happened at Rauðasandr (Red-Sand).

En fyrir því at lítit er nef várt, en breiðar fjaðrar, þá óx óþykkt með þeim Markúsi ok Inga, svá at eigi var óhætt. 
But (And) for that [reason] that our nose (head, “intelligence”?) is small, but (and) [our] feathers (spear-blades, “martial strength”?, plural) broad, then [the] discord between Markús and Ingi grew, so that [it] was not without-danger.

Markús var þingmaðr Jóns Loftssonar, Sæmundarsonar, en Ingi ok Guðlaugr váru þingmenn Hrafns Sveinbjarnarsonar. 
Markús was a Thing-person (man) (liegeman) of Jón Loptr’s-son, son of Sæmundr, but (and) Ingi and Guðlaugr were Thing-persons (men) of Hrafn Sveinbjörn’s-son.

Markús var frændi Hrafns, manni firnari en systrungr. 
Markús was a kinsman of Hrafn, one degree further to a person (man) than mother’s-sister’s-son (ie one degree further removed than male cousin).

Guðlaugr var ok skyldr Hrafni nökkut.
Guðlaugr was also related to Hrafn somewhat.

Þat var eitt haust, at Ingi fór á kynnisleit til Stakka til Guðlaugs, ok var þar nökkurar nætr. 
That was one autumn, that Ingi journeyed on a visit to Stakkar (Hay-Stacks) to Guðlaugr, and was (ie stayed) there several nights.

En er Ingi skyldi heim fara, þá ræðst Guðlaugr í ferð með honum. 
But (And) when Ingi should journey home, then Guðlaugr joined (<ráðast, Z16>) in [the] journey with him.

Í þeiri ferð váru synir Inga, Arnórr ok Magnús. 
In that journey were [the] sons of Ingi, Arnórr and Magnúss.

Ketill hét maðr, Árni ok Þormóðr, er í þeiri ferð váru. 
[There] was a person (man) called Ketill, Árni and Þormóðr, who were in that journey.

Þeir fóru um tún í Saurbæ.
They journeyed across [the] home-meadow in Saurboer (Mud-farm)

Ok er þeir váru komnir í túngarð, þá kom kona nökkur í stofu, sú er úti hafði verit, ok mælti: "Nú fara þeir Ingi hér í tún." 
And when they were (had) come to [the] home-meadow-fence, then some woman came into [the] sitting-room, that-one (ie she) who had been outside, and spoke: “Now they, Ingi [and co] journey here into [the] home-meadow.