I'm the original owner of my 98 and I haven't gotten a thing from them on this. I did get the transfer case recall on my 07 though.
Like I said, if you are concerned get not just a hitch, but a skid for the tank. It's a no brainer they should have been STANDARD....
A friend of mine has a Mercedes G-500 that has a tank design very similar to the ZJ (look under one and see). Those had the skid standard. Not all had the hitch though.
Oh and the question on MPG on the 5 speed ZJ, unloaded it might get as much at 22, my 4 speed auto one gets between 19-21. Towing I bet it would not get more than 12-15.
2007 WK Limited Hemi QDII
1998 ZJ Laredo 4.0 Selectrac