Quick and dirty
CLong, if you will drop the pan, and use a 1/4 " allen wrench as a 'feeler gauge' you can do a rough band adjustment.
On the drivers side of the trans, just above and slightly forward of the shift lever you will find a 3/4" locknut on the adjustment stud or bolt. The end of the bolt will probably be a large Torx recess, if your truck is an earlier model it may be a square drive. This adjustment is for the fixed end of the band or the anchored end.
Either way, just loosen the locknut and back it off several turns without letting the stud turn. With the pan off on the opposite side of the trans there is a lever about 3" long that has a servo and pushrod at the end of the tapered lever. This lever is the apply pressure for the band and the servo is just a piston with a rod in the center that pushes on the lever. Pull down on the lever it should only move about 1/4" before it clamps the band tight. If your's is real loose then turn in the adjustment stud untill your 1/4" allen wrench is just barely able to fit between the lever and the servo push-rod.
Tighten the lock nut on the adjustment stud and you should have second gear again. Now it is possible that the bar the lever pushes against to apply pressure to the band fell out if it was way-way out of adjustment, if so you will have to put it back in place before making the adjustment.
I hope the above makes sense, if not PM me and I will give you more info.
Hope this helps, Greg L. The Noise Nazi