I didn't have one for a 98, but I had one for an A5. The kit itself was nice, and easy to install. The instructions were pretty much non-existant, but if you know how to take apart your gun it's not difficult.
I did not use the RAP4 magazine that came with the kit, I through on a DMAG magwell and used that instead. DMAGs will work with the 98 kit as well, but you do have to buy the different magwell in order to use them.
The kits come in stock on RAP4's website periodically. Another good place to check would be www.rockstartactical.com
But it seems like when they get them, they only get a couple at a time so they go very quickly.