Loren, keep the GT, seriously. Mopeds can be had for pocket change compared to what that GT is worth. Scour craigslist for 'peds, watch the board here, and I'll keep an eye out for you too. I think you just want a toptank, not nessecarily a Magnum. Are you ok w/ step-throughs like a Maxi or a sweet looking Pinto/Swinger? Come by a fix-it day, see everyone's 'peds, maybe ride a few if they'll let you. (I know I owe you a ride for sure) See what you like, and then ask who's got stuff for sale.
Also, as you're a carless man, the GT is a much better replacement than just a moped. Yes, you can go carless on a moped, but you're gonna be going verrry sloooow, and you won't have nifty topcases and modern reliability. (speaking generally, of course)
Moped+GT. It's the way to be.