I've performed this several times on harpsichord. It's much (MUCH) easier on harpsichord than piano, but it sounds like you don't have a choice (but I'll just ask, are you positive?? there are people out there with instruments who'd loan you one-- heck, you could use mine). But if you have to use piano, and it's only the first movement, you can do it if you're fast and your scales are good (I would not do the 3rd mvt on piano). BUT, if you find that you will get to use a harpsichord after all, don't learn it on piano first and then switch for the concert! Don't ask me why I bring that up, either...
Most important: learn the cadenza first (like tomorrow) and memorize it immediately, even if you're going to use music for the concert. A lot happens harmonically, and it's easy to get turned around unless you know it (the cadenza) extremely well, plus you want to be able to watch your hands for the flying leaps.
I don't know what to compare it to, I'm afraid. It's physically not too hard if you're fast and have really strong scale work. It will be harder on piano, though, and musically there are a LOT of decisions to make, which takes time and effort. I mean, all the possibilities are not immediately obvious; I think the piece requires a lot of thought. It's fantastic music. I think it's worth giving up a little practice time on solo repertoire to learn this.