many threads started on this...
Good places to look...occasionally here...
From there... TDIClub often has motors and or entire swap cars/wrecks to use...
another good source is
www.car-part.com allows you to search regionally, or nationally and even into canada I believe.
Prices vary...early AHU/1z can go from anywhere from 600-1200 for a longblock to a complete motor with pump, manifolds, turbo, etc...
Complete MKIV ALH 1.9 TDIs go for anywhere in the same range for a bare longblock used all the way up to 1500-2000 for the motor alone... minus the ECU, wiring, cluster, etc. that is required on 02 and newer cars (unless you do IMB defeat)
Complete swap cars/wrecks to utilize wiring, etc. are the best way to go for a complete electronic swap IMO as you buy the entire car...for a not so bad price alot of times... (2500-4500 depending on year, etc) and then you have everything you need as well as parts to sell from the interior, body, etc. that can help you get some of that money back...
Takes time and some good shopping around but really good deals are out there... When I do the TDI in the B3, I might look for a "swap" car...if i go electronic
Joe