Here’s my translation

Alan

En það sama kveld er þeir Þorkell höfðu drukknað um daginn varð sá atburður
But that same evening when (or that) they, Þorkell (and co) has drowned during the-day, occurred that event (ie it so happened)

að Helgafelli að Guðrún gekk til kirkju þá er menn voru farnir í rekkjur og
at Helgafell that Guðrun went (walked) to church when persons (men) were gone to bed and

er hún gekk í kirkjugarðshliðið þá sá hún draug standa fyrir sér.
when she walked into the-churchyard’s-gateway then she saw a ghost stand before her.

Hann laut yfir hana og mælti: "Mikil tíðindi Guðrún," sagði hann.
He bowed-down (lúta) over her and spoke: “Great (important, grave) tidings, Guðrún,” he said.

Guðrún svarar: "Þegi þú yfir þeim þá, armi."
Guðrún answers: “Keep-you-silent about them then, wretched (one).”

Gekk Guðrún til kirkju svo sem hún hafði áður ætlað og er hún kom til
Guðrún walked towards (the) church just as she had before intended and when she came to

kirkjunnar þá þóttist hún sjá að þeir Þorkell voru heim komnir og stóðu úti
the-church then she bethought-herself to see that they, Þorkell (and co) were (had) come home and stood outside

fyrir kirkju. Hún sá að sjár rann úr klæðum þeirra. Guðrún mælti ekki við þá
in-front-of (the) church. She saw that (the) sea (ie sea-water) ran out-of their clothing. Guðrún spoke not with them then

og gekk inn í kirkju og dvaldist þar slíka hríð sem henni sýndist.
and walked inside into (the) church and remained there for such time as to her seemed-fit (sýnast,, Z2).

Gengur hún síðan inn til stofu því að hún ætlaði að þeir Þorkell mundu þangað gengnir.
She walks after-that inside to (the) sitting-room because she expected (supposed, ætla, Z1) that they, Þorkell (and co) would (be) thither gone (past part).

Og er hún kom í stofuna þá var þar ekki manna.
And when she came into the-sitting-room, then no persons (lit: none of persons) were there.

Þá brá Guðrúnu mjög í brún um atburð þenna allan jafnsaman.
Then Guðrún was much amazed (lit: (it) caused-to-move (bregða) in the brow for Guðrun, impers expression, see brún, Z2) about this event (taken) all together.

Föstudag hinn langa sendi Guðrún menn sína að forvitnast um ferðir þeirra Þorkels,
On Good-Friday (lit: the long Fast-Day), Guðrún sent her persons (men) to enquire about their journeys (movements, plural), Þorkell’s (and co’s),

suma inn á Strönd en suma um eyjar. Var þá rekinn víða kominn um
some in to Strönd (the-shore) but (and) some around the-isles. The-material-driven-ashore was (had) then (ie at-that time) come (reached) widely around

eyjarnar og svo til hvorrartveggju strandar. Þvottdaginn fyrir páska
the-isles and also to each-of-the-two shores. On the-Saturday before Easter

spurðust tíðindin og þóttu vera mikil því að Þorkell hafði verið mikill
the-tidings were-heard and was-reckoned to be great (significant, grave) because Þorkell had been a great

höfðingi. Þorkell hafði átta vetur hins fimmta tigar þá er hann drukknaði en
chief. Þorkell had eight winters of the fifth-ten (ie fifth decade) (ie he was forty-eight years old, eight years into his fifth decade) when he drowned but (and)

það var fjórum vetrum fyrr en hinn heilagi Ólafur konungur féll.
that was earlier by four winters than the holy King Ólafr fell (ie died).

Guðrúnu þótti mikið fráfall Þorkels en bar þó skörulega af sér.
Þorkell’s death was-reckoned great (important) to Guðrún (ie she took it much to heart) but nevertheless (she) bore (it, ie the hurt) bravely from herself (?).

Fátt eina náðist af kirkjuviðinum.
Little only was caught (ie recovered, pp of nást, under ná, Z2) of the-church-timber.

Gellir var þá fjórtán vetra gamall. Hann tók þá til búsumsýslu með móður sinni
Gellir was then (at that time) fourteen winters old. He began then management-of-the-farm (estate) with his mother

og tók við mannaforráði. Var það brátt auðsætt á honum að hann var
and received authority (ie as chieftain). That was at-once easily-seen in him that he was

vel til fallinn til fyrirmanns. Guðrún gerðist trúkona mikil.
well fitted (worthy, see fallinn, Z2) for chieftain (fyrirmaðr, Z1). Guðrún became a great woman-of-faith (seems more appropriate than confidante, Z´s gloss).

Hún nam fyrst kvenna saltara á Íslandi. Hún var löngum um nætur að kirkju á bænum sínum.
She learnt (nema, Z7) (the) psalm book, first of women in Iceland. She was continuously during nights at her prayers (boen, fem pl, not bær).

Herdís Bolladóttir fór jafnan með henni um næturnar. Guðrún unni mikið Herdísi.
Herdís Bolli’s-daughter went always with her during the-nights. Guðrún loved Herdís greatly.