How do I get out of retail sales when it's all I've done for so many years?

I'm a guy in his thirties who has only done this kind of work since after high school, and now that I'm bored to tears with it and find it unrewarding, I'm beginning to have problems standing for so long!! I have a fine arts degree from a good university, but since I have virtually no administrative skills (like Excel, etc), the temp agencies won't even talk to me. I'm starting to actually feel jealous of people who have 9-5 jobs in offices! I'm great with people, but I DREAD being destined to just work in a store for the rest of my life.