That being said, I don't know how to read Swedish. Suggestions for where to turn to for help? I do know that one of the involved men was a "mega-barn" builder, a term which I can not find ANYWHERE. Is this a real thing? Is that just an extra big barn?
Hi OP, for translation help, if you don't get answers here, you might try /r/Swedish, or one of the translation subs, /r/translation /r/translator.
You could scan and post the letters here. There are quite a few regular contributors on this sub who speak Swedish, me, /u/vonadler (who might actually be old enough to have written these letters) and a few others that I know of.