It's do-able. I did it the first time all by myself, and I'm just a scrawny out-of-shape 164-pound 5'9" shrimp of a dude. Second time, I had a buddy hold up the tail end and keep the exhaust pipes out of the way while I lifted the front and maneuvered it into place. Did about the same thing when we serviced the throwout bearing on Frankenstang's '04 V6 'stang, and she helped a lot.
As I remember it, the best position for lifting it up there by yourself is to lay on your back with your head towards the front of the car and your feet right toward the back. Sort of play "airplane" with the tranny by supporting it on your hands and knees. It's not THAT heavy, really - I think a T-5 only weighs around 75 lbs., and it only holds a little over 2 quarts of fluid - and it CAN be done solo, but having a second pair of hands just makes things go a LOT easier.
FWIW, I would NOT try doing things alone if you're dealing with an AOD or any other automatic. A guy I worked with tried benching up a C-4 into his car once and wound up dropping it onto his chest, cracking a couple of ribs - he was lucky to be able to roll the thing off himself, or it would've suffocated him. A tranny adapter for your jack or a dedicated transmission jack should be a minimum requirement for an AOD drop/install, and a second (or even a third) pair of hands a very strong recommendation.
when i put the rebuilt aod in my car i have a few buddies help me becasue it such and akward wight to lift up and slide into place.. the clutch on my dads stang is getting replaced this coming winter. a T-5 will be a brezze compared to getting that aod up in there..as long as the bolts come lose.