A real detriment to recognition of the car as a collectible by VW buffs is the technology used in the Type 4.
If you know someone who can even spell "Eberspächer" you're really lucky. The unit is not bad at all, but if it fails and you end up knowing zero about it you'll most likely run into all kinds of people preaching about the fire hazards of gas-electric heaters. I say: These people have no clue. Like with anything, the right maintenance is the key. Any automobile will blow up one day if those precious rubber fuel hoses are left to rot and crack. For those who like to believe their own good senses instead of clueless people I put up scans of a gas-heater repair manual for the Eberspächer BA4, the model used in the VW 411 and 412. Parts for it are not available any longer. I have seen some for sale at VW swap meets and no junker I ever came across missed theirs. Because they're a bitch to get at...
Up until 1973 the Bosch D-Jetronic prepared the right gas/air-mixture. This system relies on a vacuum-sensor, which is connected to the intake manifold and measures the air pressure inside (hence also called "vacuum controlled" fuel injection), to get an accurate picture of how the engine is doing and how much fuel it needs. There are a obviously a few more sensors involved, but this vacuum-control sensor is at the heart of every D-Jetronic. The Bosch D-Jetronic has a very bad rap. People were sent from VW shops to Bosch shops and back because few people can work with the system. Some information is in the combined L- and D-Jetronic manual, follow the link to see the scans. Tim's 914 Fan Page has a very good page at www.914fan.net/djet.html. Even though it is Porsche 914-specific there is a lot of good general information. I remember the legendary "Idiot Book" by John Muir has a few paragraphs about it as well since John writes a little about fuel-injected Type 3s in his book. For parts consult your nearest Bosch distributor or salvage yards in the area. Keep in mind that some VW Type 3s (the 1600 models with fuel injection) had the same system from 1968 till the end of production. Porsche 914s used the D-Jetronic on some of the 4-cylinder models as well, specifically the 1.7 liter built from 1970-73 and the 2.0 in 1973 and 74. After that Porsche decided to switch to the L-Jetronic (thanks to Jeff Bowlsby for this information).
The second kind of fuel injection used in the Type 4 is the L-Jetronic. Instead of a manifold pressure sensor it employs a so-called air flow meter to guess at the engine's fuel needs. Hence its other name "air flow controlled" fuel injection. The air flow meter is a pretty simple device that sits in the stream of air coming into the manifold and measures its amount with the help of a flap. The flap is spring-loaded and the degree of opening corresponds to the amount of air flowing into the manifold. This system was used on Type 4s in 1974 only. It is a little simpler to maintain and tune, but if the engine backfires into the intake manifold the little old flap is usually toast. For an overview and a troubleshooting guide refer to the L-Jetronic manual. For parts refer to your Bosch dealer or the salvage yard. Some parts are interchangeable with the L-Jetronic available for VW Beetles after 1975 and in the VW Buses with L-Jetronic. The air-flow meter, however, is a Type 4-only part, nothing else than the Type 4 part will fit. Believe me, I've tried every air flow meter available for aircooled VW engines, i know.
The automatic transmission is something I would have a real trans shop worry about. A lot of small parts are still available from VW, like switches and pressure sensors as well as gasket kits.