86-89 use one key type
90-92 use a different key type
86-88 use one type of hatch cylinder
89-92 use a different type (different tails)
So yes, you can use a newer lock cylinder set in your car, but the hatch cylinder will only work 100% correctly if you are using the newer tails, if not you may have to try to modify it to work.
As for availability of the sets, if anything is still available it will only be in grey and/or shadow grey, all other colours change up (this only really applies to the glove box lock). That being said, I was under the impression (and I quickly checked a few numbers) that all lock sets are obsolete at this point. If you can get one, go for it, because it will be one of the last if you can get it at all.
Why do you even need an entire new set? Individually most cylinders are still available, why not just get the one or two you actually need and get them rekeyed to your code?
Jeff