I think making your first post should come with a mandatory "I'm from...."
I have no real idea what your injury entails, but if you can't run (impact) or bike (posture) anymore you should probably be asking these questions to your doctor - sorry to say but it sounds like a "no". Top-roping I think should be ok-ish - depending on your injury. The impact from falling is very low and you can have great fun doing it.
Good idea? Maybe - check with your doctor, preferably one that has some clue about climbing. He / she would then be able to give you an informed opinion about your risks. I'm sure if you could climb grade 20 + you'd delight Snort by climbing steep stuff where a good belayer would be able to catch you softer than falling down on your bed, even on lead.
Buy the gear? - If your doc and / or your common sense allows you, yes, shoes first (it's the gear no-one really wants to lend to you, and after all, it should be the one piece of gear that fits you as well as possible). But then again only after you've had a casual day (or 5) out with some regulars and have a clue what it's about and decide to continue with it.
Find a group of people? Usually pretty easy if you divulge your general location
Hope it helps a little!