I tow a 400 lb trailer about once a week with my Budget Boosted WJ with few problems. Your back end will most definitely sag but that's nothing airbags won't fix. With your setup you shouldn't have any problem. Just be gentle going over bumps so you don't bottom her out too much because I can tell you from experience your bumpstops will begin to crush then you have problem with the exhaust rubbing on your brake line and abs line. I ended up putting extended bumpstops in the back and that fixed my problem. The second issue I ran into was my steering was sloppy when I was towing so I upgraded my steering stabilizer to a rough country stabilizer then added a second one from Kevins Offroad and put a Rough Country stabilizer to that one as well. The steering has improved quite a bit from that. The only real way to make sure is to tow a good 100 miles then get under and check the lift components and undercarriage very well and make sure all your bolts are still in torque. If all is well tow another 500 miles then take it to a ASE mechanic and get him to ok everything. After that you should be good just keep an eye on the lift components. After a while though your rear springs will begin to squat and you will want to replace them. A way around this is to use In Coil Airbags when you tow.
2001 Jeep Grand Cherokee (WJ) Laredo, 4.0L, L6, 4x4
2" Rough Country Lift, 245/75/16 Firestone Destination A/T's, 100% Straight Piped, 10" Kicker Comp Woofer, 10" Ported Kicker Truck Box, 250.1 Kicker DX Amp, JVC Head Unit, Spectre Intake