Yeah I hear a lot of people tell me their mechanic said it would be too hard and cost ridiculous amounts of money.
Let you in on a secret mate. I sell mpfi kits for $150 each here in Perth, or $300 fitted.
Most of the work is involved in changing the manifold - simple bolt off, bolt on stuff. Time consuming is all.
The wiring involves one wire change for the new idle control mechanism, and another three for the gearbox computer if it's a 4-speed. 3-speeds and manuals do not require that.
Changing the wiring is as simple as plugging in the MPFI injector loom that comes with the manifold, and running an extra wire or 4. As Jase said, there's an article on the site, actually written by my brother I think (can't remember
As above, a nice cam can be relatively cheap and return good figures on the MPFI setup. You'll want a proper (not just cat-back) exhaust to make the most of it though. Probably the thing to do before a cam.