http://www.paralympic.ca/english/ath...NNOR_EARLE.asp
I've seen Earl train in the gym (when I used to train in the varisty gym with national team athletes). He generally does dumbbell work (for instance, I have seen him do dumbell cleans) and any seated upper body stuff is fine. He does have more than two prosethetic legs though (though I've only really seen him in the Flex foot one when he races. In the gym, he's wearing track pants). He also does use the leg press machine. Since he's an AK amputee, his main strength work on his amputated leg is around the hip joint. This would obviously be different for you.
I think the key here is to take this step by step. You've been through a very serious illness and it's best to go a bit slower at first. Also, you will have to adapt (more than just comfort) to the prosthetic for exercise--the amputation site will still likely be prone to breakdown at first if you over-do things, especially if the socket doesn't fit just right.