Our 2000 J G Cherokee 4.7 liter V8 (same engine in the 2006) pulls our 23 ft no problem at all. Our towing capacity is 7000 lbs. I would feel comfortable in pulling the 28 ft if needed.
If you have the V6 then the towing capacity is 3500 lbs.
For car spec's go to
2006 Jeep Grand Cherokee
If you decide to put a hitch on, make sure you add a transmission cooler. This is very important.