Its easy, get a freon can adapter.$8. its just a valve and hose that hooks the freon can to the low side shrader valve.hook the can up and turn the valve with the truck running and if the compressor dosn't kick on,jump it for a minute and see if it takes the freon.hold the can upright and shake it a little while installing.if the freon is going in the system properly,the can will get cold in your hand.134A is only about $6 a can.off hand I would say to get at least 3 cans.Put one in and see if it gets cold,then put another,then another until it get as cold as you want.My 95 model with 2.3L is blowing 39 degrees out the front vent(checked with digital thermomitor).