Here’s my translation

Alan

Síðan fló Bósi belg af þeim báðum ok fór síðan til skips, ok sögðu Smið, hvat þeir höfðu afrekat. 
After-that Bósi flayed the skin from them both and journeyed after-that to (the) ship, and said to Smiðr, what they had accomplished.

Þeir gerðu nú ráð sín. 
They now made their plans (sín is reflexive so refers back to þeir).

Smiðr færði Bósa í aðra nágrímuna, en fór sjálfr í aðra ok í þann búning, sem sveinninn hafði haft, en Bósi í þann, er Sigurðr hafði átt.
Smiðr conveyed (fitted, helped, foera) Bósi into the-one (ie the first) dead-man´s-mask, but (and) (he) himself went into (ie put on) the-other (mask) and into (ie put on) that attire, which the-servant-lad had had (ie worn), but (and) Bósi into that, which Sigurðr had had (ie worn)

Þeir sögðu Herrauð fyrir allt, hversu hann skyldi bera sik at, ok fara þeir nú heim til borgarinnar ok kómu at þeim hallardyrum, sem Goðmundr konungr var fyrir. 
They prescribed for Herrauðr completely, how he should carry himself at (it) (ie what he should do), and they go now ‘home’ to the stronghold (‘castle’) and came (ie arrived) at that hall-doorway, which King Goðmundr was before (ie in-front-of).

Þóttist hann þar kenna Sigurð, ok fagnar hann honum vel ok leiðir hann inn, ok tók hann þegar við féhirzlum konungs ok ölgögnum ok kjallara ok hefir skipan á, hvert öl fyrst skal ganga, ok segir byrlurum fyrir, hversu ákaft þeir skulu skenkja. 
He bethought-himself there to recognise Sigurðr, and receives him well and leads him inside, and he (ie Bósi-as ‘Sigurðr’) received at-once (control of?) (the) king´s treasure and (the) drinking-vessels and (the) cellar and has (ie takes) charge over which ale shall go first, and says to (the) cup-bearers, how fully (ie liberally, the maximum extent to which) they shall  pour-out (the drinks).

Sagði hann, at þat varðar mestu, at menn verði it fyrsta kveld sem drukknastir, því at þar eimir lengst af. 
He said, that that matters (varða, Z3) most, that folk (men) should-become as drunk-as-possible on the first evening, because there- from (ie from that) (the) vapours (intoxication?) lasts-longer

Þessu næst var höfðingjum í sæti skipat ok brúðrin inn leidd ok á bekk sett ok með henni margar meyjar hæverskar.
Thereupon (it) was arranged for (the) chieftains into (their) seats (ie the chieftains where shown to their seats) and the-bride led inside and set (ie placed) on (the) bench and with her many well-mannered (classy) maidens.

Goðmundr konungr sat í hásæti ok brúðguminn hjá honum. 
King Goðmundr sat in (the) high-seat and the-bride-groom beside him.

Hrærekr þjónaði brúðgumanum. 
Hrærekr waited-on the-bride-groom.

Eigi er greint, hversu höfðingjum var skipat, en þess getr, at Sigurðr sló hörpu fyrir brúðunum. 
(It) is not recorded, how (it) was arranged for (the) chieftains (ie the seating arrangements for the chieftains), but (it) mentions that, that Sigurðr struck (the) harp for the-bridesmaids (plural, brúðr, Z2).

En er minni váru inn borin, sló Sigurðr svá, at menn sögðu, at eigi mundi fást hans líki, en hann kvað þar lítit mark at fyrst. 
But (And) when toasts (minni, Z4) were carried in, Sigurðr struck (ie played the harp) in such a way, that men said, that his like (equal) would not be-gotten (found), but (and) he declared there (that?) a small token (proof of his abilities?) at first (ie for starters?) (ie he was only just warming up?)

Konungr bað hann eigi af spara. 
(The) king bade him not to hold back (lit: spare from (it))

Ok sem inn kom þat minni, sem signat var Þór, þá skipti Sigurðr um slagina, ok tók þá at ókyrrast allt þat, sem laust var, hnífar ok borðdiskar ok allt þat, sem engi helt á, ok fjöldi manna stukku upp ór sínum sætum ok léku á gólfinu, ok gekk þetta langa stund. 
And when that-toast came inside, which was dedicated to Þór, then Sigurðr changed the-(harp)-stroke, and all that which was loose (ie not nailed down) started then to bestir-itself (úkyrrast, refl verb), knives and table-plates and all that, which no-one held on to, and a great number of folk leapt up out of their seats and waved to-and-fro (leika, Z3) on the-floor and this went (on) for a long time.

Því næst kom þat minni inn, er helgat var öllum Ásum. 
In that next (instant) that toast came inside, which was ‘hallowed’ (ie proclaimed reverently) to all (the) Ásir (old heathen Gods).

Sigurðr skipti þá enn um slagina ok stillti þá svá hátt, at dvergmála kvað í höllunni. 
Sigurðr changed then yet (again) the-(harp)-stroke and tuned (stilla, Z4) that so high (in volume or pitch?), that (it) sounded an echo in the-hall.

Stóðu þá upp allir þeir, sem inni váru, nema brúðguminn ok brúðrin ok konungrinn, ok var nú allt á ferð ok för innan um alla höllina, ok gekk því langa stund.
Then all those who were inside stood up, except the-bride-groom and the-bride and the-king, and now (it) was now everywhere (allt, Z2) on a ‘trip’ and procession (för, CV) internally around all the-hall, and (it) went in that (way) for a long time.