Wait, I'm confused here.
The car acts like its in Neutral, but the speedo is still increasing?
Also, since you stated that it still seems to engage all the gears, I'm guessing its more of a clutch problem. Unfortunately that means dropping the tranny too.
In terms of selling the car, your best course of action would be a new transmission. Might as well replace the clutch while you're in there.
Sorry to hear about it. That sucks!
