Perhaps someone on the Sweden forum will translate the letter for you, if it is not too long. There are quite a few Swedes who read and help on that forum. I have seen several posts where someone asked for a translation and then received a reply from a Swede willing to help. You will probably need to scan the letter and send it as an attachment to someone who offers to help. (If you post it online, that is another option.)
Type Sweden into the "Jump to Forum" space at the top right of this page.