Just follow lawnboy's advise.........all you need to do is provide and "edge" to the perimeter for the pavers. You could do this with "grouted" units. This is ok, cuz if it fails due to the moisture problem, it isn't a big deal to redo. I would allow for some weep holes so that moisture can get thru the perimter.
By the way, this slab is really a good thing as long as it is on stable soils. If you have lots of heaving in your area due to clay soils, then your slab may crack........or, if it wasn't installed correctly. If it was, and it has been there for a long time and hasn't had a problem, then your worries are probably over. You could probably grout your pavers directly over the slab. However, personally, I would go with the perimeter pavers and put the others directly on the slab and sand the joints.
There are numerous sites and "help" files at your local lawn and garden center on this.
Good luck, and invite us over for a party on the new patio. BEG