Here’s my translation

-          not without its challenges…

Alan

Þórir þóttist svara að honum þótti þetta of lítið af svo nánum frænda og féríkum og lést eigi aftur munu hverfa við litla fémútu.
Þórir bethought-himself to answer that this seemed to him too little from such a near and wealthy kinsman (dat singular of frændi) and declared-of-himself (látast, z13) (that he) will not turn back with (ie for the sake of) a little financial-inducement (bribe)

"Vissi eg ei," segir Þórir, "að tröll væri mér svo nær í ætt áður þú sagðir mér. 
“I knew not,” says Þórir, “that a troll was so near to me in pedigree before you spoke to me.

En engrar eirðar ættir þú af mér von ef ei væri frændsemi með okkur."
But (And) you would-have (subjunctive of eiga) expectation (hope) of no mercy (genitive) from me if (there) was not kinship between us.”

Agnar segir: "Seint munu þín augu fyllt verða á fénu og því máttu vorkynna mér," sagði Agnar, "að mér þyki féð gott því að þú munt ærið mjög elska féð áður lýkur."
Agnar says: “Slowly your eyes will become (ie be) filled by means of (á, z4) the-money and you-are-able-to excuse (várkynna) me for that,” said Agnar, “that the-money would-seem to me good because you will sufficiently (oerinn) much love the-money before (it, this affair?) concludes.”

Þórir segir: "Ekki hirði eg um illspár þínar. 
Þórir says: “I care not about your evil-prophesy.

En þiggja vil eg að þú vísir mér til meiri févonar ef þú vilt þitt fé undan þiggja."
But (And) I will accept that you show (direct) me to a greater expectation-of-money (féván) if you want to set-free (release, splash out) your money.”

"Heldur vil eg það," segir Agnar, "en deila illdeildum við þig. 
“I want (vilja) that rather,” says Agnar, “than to deal (ie occupy myself, delia, Z4) with hostilities against you.

Valur hét víkingur er átti gull mikið. 
(There) was a viking called Valr who had much gold.

Hann bar féið undir helli einn norður við Dumbshaf og lagðist á síðan og synir hans með honum og urðu allir að flugdrekum. 
He bore (carried) the-money under a cave alone in the north close-to Dumbshaf (Dumb’s-Sea) and (he) fell-upon (it) (leggjast á e-t, Z15?) afterwards and his sons with him and (they) all became flying-dragons.

Þeir hafa hjálma á höfðum og sverð undir bægslum. 
They have helmets on (their) heads and swords under (their) (dragon-) shoulders (bæxl, CV),

Nú er hér kálkur er þú skalt drekka af tvo drykki en förunautur þinn einn drykk en þá verður eftir það sem má."
Now here is a drinking-cup (goblet, kalkr in Z rather than kálkr) which you shall drink from two draughts but (and) your travelling-companion one draught but (and) then that which may (be) becomes after (ie is (left) behind) (ie whatever remains behind ie ‘undrunk’ so be it? With the implication that it should not be drunk.)”

Síðan vaknar Þórir og voru þessir hlutir allir þar í hjá honum er Agnar gaf honum. 
After-that Þórir awakens and these things were all there-in beside him which Agnar gave him.

Ketilbjörn vaknar og hafði heyrt allt þeirra viðurmæli og svo séð hvar Agnar fór. 
Ketilbjörn awakens and had heard all of their conversation (viðrmæli) and also (had) seen where Agnar went.

Hann bað Þóri taka þenna kost. 
He asked Þórir to take this choice (chance, opportunity).

Eftir það tók Þórir kálkinn og drakk af tvo drykki en Ketilbjörn einn. Þá var enn eftir í kálkinum. 
After that Þórir took the-goblet and drank off two draughts but (and) Ketilbjörn one. Then (there) was yet (more) (left) behind in the-goblet.

Þórir setti þá á munn sér og drakk af allt.
Þórir placed (it) then to his mouth and drank off (it) all.

Nú féll á þá svefn. 
Now sleep fell on (overcame) them (þá).

Agnar kom þá enn og ávítaði Þóri er hann hafði allt úr drukkið kálkinum og kvað hann þess drykkjar gjalda mundu hinn síðara hlut ævi sinnar. 
Agnar came then yet (again) and rebuked Þórir that he had drunk everything out of the-goblet and declared he would pay for (suffer on account of) that draught (ie the bit left behind) in the later part of his life (ævi).

Agnar segir þeim fyrir marga hluti þá er fram komu síðar og lagði ráð til með Þóri hversu hann skyldi vinna hellinn Vals víkings.
Agnar predicts (segja e-t fyrir) for them many things, those which came forward (ie came to pass) later and furnished advice to Þórir how he should reach (vinna, Z11) the-cave of (the) viking Valr.