36' 5th wheel and 30' TT are going to be very similar in overall length (front truck bumper to rear trailer bumper). Lots of good info so far and I generally agree that you can put the 5th in the same space as the TT.
Everyone's got their method of backing up so just go with what works for you. My DW is an amazing woman in many ways but helping me back up an RV just isn't one of them. I go it alone and am fine with it. I congratulate those of you who can tag team it. I imagine it works out quicker/better in the end. Being alone in backing into spots, I just get out of the truck and evaluate several times, if needed. Of course, turning to the driver's side is way easier but turning the other way isn't bad. Just a few times getting out and getting a good line and I'm all set.
OP, if a 30' TT can fit, your 36' 5th will make it too... it just may take a bit more time and patience.