Hugs and prayers on the loss of your mom.....mine is 81 now and I just dread not having her around....even if she lives a long life it's not going to be enough time to suit me.
First of all, I'd try to neaten some, but I would wait until you're in a good emotional place to be objective about what you want to keep and what you want to get rid of. Then, maybe think about things or organizations that meant alot to her and either donate to them or sell them and give the proceeds to that organization or charity or church. I know it's hard to live with the disorganization but don't part with something you'll wish later you kept.
Smile....you've got lots of friends here....