If you do indeed need a new PCM:
Junk Yard or e-bay are probably the cheapest bets. The PCMs are year, engine and drivetrain (4x4, 4x2) specific. You need a 01, 5.9, 4x4 PCM. Note I assume you have the factory alarm, then there is no problem. If you do not have the alarm, the vehicle the PCM comes from CANNOT BE FACTORY ALARM EQUIPPED.
There are places that sell refurbished PCMs search
http://www.durangoclub.com/forum/ There was a guy that had PCM issues and go a used one from some company. Check Advance Auto's site. I believe I saw that they sell them.
If you must by new get it from
http://www.dodgepartspro.com/ or
https://www.dodgeparts.com/ (call each one. it's easier that trying to use the site)They will be far cheaper that your local dealer. These sites are just Dodge dealers. You can try showing your dealer the price you can get it for and see what they can do.