I don't have experience with the long-nose vans, so issues like the mounts and wiring will be different. My advice would be to look at a lot of diagrams on vagcat.com and determine the similarities to the short-nose vans where this has been done several times (mostly in Europe).
Wiring is not difficult if you are capable of reading schematics, especially Bentley-style. Wiring simply consists of routing each signal where it's intended to go; if the sender and receiver are compatible, it will work. It remains up to you to determine if that's the case between, say, an AHU coolant temperature sender and a 2002 gauge cluster. With the short-nose vans this is a matter of plugging things in correctly and swapping pins in plugs, not cutting and splicing.
The EDC system is very much self-contained, wiring wise, so retaining climate control and ABS should be straightforward. I can't comment on the physical cluster fit, but if they are not the same as the B4 (the A3 will almost certainly not fit) I would retain the T4 cluster and condition the signals to work. For my swap this involved re-writing the EEPROM inside the cluster to support the correct 4-cylinder tach and VSS, but a popular option on the TDIClub is some frequency-conversion box from Dakota Digital. I imagine a $4 arduino clone would do as good a job if you're willing to learn and write 10-20 lines of code.
Your parts list is missing the ABL inner timing belt cover, which is required for the ABL (not AHU engine mount bracket). You may also want ABL bellhousing tins since they are different when mating to an 02B vs 02A. I ended up fabricating them, but it would have been cleaner to have something to bolt on.
To my knowledge-- which is limited on the later stuff-- an ALH style block (I forget the block code) was never offered, so factory mounts wouldn't be available.
You can go through my swap at andrewclink.com/projects/thebus . Things like power steering and AC connections have to be considered, airbox, intercooler piping, exhaust, etc. So worth it in the end (at least coming from a doggy 5-cylinder), but a lot more work than you might think at first.