Discos are fairly simple to work on as well, but you will be dealing with just as many issues. Engines in the D2 are notorious for block failures as well as the top end. A lot of people have overheating issues and have the headgaskets redone without knowing the block is cracked, liner has slipped, and continue having engine problems. It's hit or miss, but I would ONLY buy a D2 from an enthusiast by keeping an eye on the classified ads of various forums. If you are lucky you can find a well maintained D2 with a rebuilt engine maybe including top-hat liners and you won't have to worry about the engine too much. But you are on the right track with a CDL equipped 2004 and the bigger 4.6L engine. If you buy one from a soccer mom you will have your hands full and break your bank trying to update every mechanical part that is now on its way out, and expect operating temps to be higher than normal and a CDL shifter linkage that is frozen from lack of use. So like I said, be patient and wait to buy a D2 from a true enthusiast which has been maintained, lifted, etc.
PS: temperature gauge on instrument cluster is basically a 3 position switch that has cold, neutral and hot settings. many soccer moms and HS kids drive these trucks hot for days on end until there is a full blown cooling system failure because they don't know any better. An aftermarket temp gauge should be your first purchase/project if you end up with a model that has not been modified with this. Test drive any vehicle and absolutely have some hardware on hand that you can plug into the OBD under the dash so you are able to monitor operating temps under all conditions, as well as check for fault codes and system readiness. We have heard of people disabling lamps/bulbs in dash for ABS and CEL faults! I've read horror stories of people buying a D2 and overheating on the way home from the dealer... Having to add water on side of road, finding bulbs broken/removed from dash cluster. Too many problems with these trucks so be wary and suspicious. Never take someone's word.
ABS problems can usually be resolved with 1)new brake pads and rotors, 2)new wheel hub and speed sensor, 3) shuttle valve replacement, 4) modulator rewire, 5) modulator replacement with known-good unit.