Does anyone know where to buy a reasonable powertrain control module in case it's decided I really need one?  

I lifted my truck twice, suspension, then bodylift  around 2006 and 2008, and the 4WD gear sits low  after the bodylift now.  Back 2 years ago, I noticed that I had to jiggle the gear to put it in 4WD in heavy snow to have the 4WD activated.  Guess I need to get the gear clutch extended somehow.  Anyway, last winter I noticed that it stopped working.  The dealer thought it was just the light not coming on is all.  

This past Monday, took it back to get it ready for winter (possible snow, if any in the DC area) and they replaced the 4wheel low button and said it was working, but the 4WD indicator light not coming on because the powertrain control module needs to be replaced and their cost is, of course, $1,200.00.  

I decided not to wory about the light, but coming home, noticed that the 4WD seems not to be working at all still as I tested it.  Taking it back Monday.  Any suggesstions?  Is the powertrain control module, which I was told is a major computer, having issues, need to be replaced?  Service advisor didn't think so, says this and that  wasn't recognizing the 4wd is activated and hence, the light isn't coming on, so the module doesn't really need to be replaced, but that the 4WD was working.  This was told to me when they called to say my truck was ready.  

BTW got some pointers from this site last year from I think member blacklight and which I printed it out, for the reasons 4WD not working.  So I need to ask the mechanic Monday if he even read the information I gave  the service manager.

When looking for a TCM & BCM for my 05 drivetrain, I used online salvage yards and paid $250 & $150 for them.  Since then I have picked up all three on CL for $300, and found a Metal Salvage with three XL7's to be smashed for scrap metal.
I would get a 01 Factory Service Manual (not the CD junk) and go over what is required to engage 4wd.
If you have that list, then post up what you have checked, what happened or didn't, or what you need clarification on.  We need more information to help you.