Dog with dislocated knee cap?

My yorkie has always had bad knees, but a few days ago, she dislocated one of her kneecaps. The vet popped it back in, but it dislocated again within hours. The vet said that if she didn't recover or if the knee kept sliding out of place, she'd need surgery. She's still limping, and her kneecap keeps sliding out of joint, so I'm assuming we're at the surgery stage. The vet said he'd give me the name of a specialist to take care of it (it's Sunday, so I have to get it tomorrow), but I'm a little worried about the cost. I'll pay for the surgery no matter what, of course, because I can't leave her in pain like this, but does anyone have any experience with this? I think the vet said she had floating patellas or something like that. How bad will this surgery be? And how long will it take her to recover? Ballpark, of course. I know it won't be the same for every vet, or even for every dog. I'm just looking for estimates.