The short answer is it depends on how much time you have to work on one and if the GL site will let you do any work on their real estate. Some will, some won't. It is usually dependent on base policy not necessarily GL. They are very paranoid about fluid spills and usually won't let you do any radiator work (change hoses), drain anything or bleed brakes (in the case of vehicles with fluid brakes). If you are recovering a truck with super singles remember that they weigh around 500 pounds each. You will prob not be changing one of them on the lot. They may allow a mobile tire man to swap one out on the lot if needed. I would bring two hot, high CCA batteries (you can get by with two verses the four stock ones). Transmission fluid, extra fuel and a way to get it in the tank without sloping it on the ground (I use a 12 volt transfer pump and a 50 gal drum). If you have a like size vehicle and a towbar you can either flat tow it home or get it off base to work on it. An airhose with a gladhand hookup is good along with a air gauge. The only thing you forget to bring is the one item you will need the most if Mr Murphy shows up. Credit card, cell phone, proper clothes for the weather and a list of folks along your route is good insurance also.