As far as the cleaning goes, as my mom always tells me, take it a little at a time. I rent out a bedroom at my mom's place (for the moment) where I sleep, eat, quilt, etc. in and it can get to be a huge mess very quickly (like it is now!). Besides not having a lot of time to get down to it, sometimes I look at it and go "There's so much to do!" If I can bring myself to do it, I start off small like clean up all the Wal-Mart bags that have accumulated (work at Wal-Mart and tend to get a thing or two after work almost every day). Sometimes I'll get finished with something and go onto another thing and next thing I know I can see a floor!
But in your case, you also have the sentimental value and the loss of your husband. I imagine the sewing room is a place with a lot of memories with your husband---looking at your purchases from a fabric store, cutting out fabric, piecing together quilt tops, getting frustrated if something wasn't going right, and basking in both of your finished works. It wasn't just your sewing room---it belonged to both of you. You might be feeling weird about going in there to do anything because the other owner is no longer around (physically anyways). And August was only two months ago so don't beat yourself up if you haven't gone in there since.
At first, I say don't even go in there with the intent on cleaning. Just step into the room. If you can manage then check out all the things you quilted together.