Actually, the reason SR20DET engines are cheap and plentiful here in Japan is probably because Nissan has used or is currently using the engine in a ton of cars, including the Silvia/180SX (240sx), Bluebird SSS (sports version of the Japanese Altima... I think most DETs in the States come from Bluebirds, since they are also front wheel drive), the Avenir Salut (a station wagon originally based on the Primera/G20 platform) and the Sunny GTi-R (kind of a hatchback version of the Sentra turned into an AWD rally car). They also use it in a few of their larger mini-van type vehicles, like the R'nessa (as far as I know, a vehicle only available here...)
I don't have any connections here in the auto wrecking business, so I can't say how much the engines cost before shipping but I'm going to start doing some research; I want to put a Sunny GTi-R engine and 6 speed tranny in my all-wheel-drive Primera... can you say G20 rally car?
As for the intercooler, what a lot of people here do is use the intercooler from a Skyline GT-R; it is a front mount and is actually for a slightly bigger engine than the SR20DET, the Skyline's RB26DETT. You're going to need to get the piping fabricated, and from what I've seen, usually cutting or replacing the front bumper is also a necessity for a proper fit. Depending on what you're putting it into, there may or may not be aftermarket front bumper covers that will fit an intercooler...