I'd think wiring it would be the big PITA. Might be pre-wired...
If I really had my heart set on that car and I had to have A/C at all costs, I'd be sure that I had access to a complete parts car. It's always the little bits that kill me on cost. Honestly, I don't think it'd be that difficult. Just an annoying, fiddly job.
I'm not sure of your mechanical skills, but if you have the guts to tackle this yourself it'd save you a ton of money. An r134 recharge is cheap (about $80 'round here), and the only parts you'd need to have are a new $25 receiver/dryer and some o-rings & ester oil. I haven't done a conversion myself, but it's on the eventual list. I'll share some pics if/when I get to it.
You could also use a few of the aftermarket r12 substitutes to fix up an old system. Someone will chime in with suggestions.
I'm not trying to jack the thread, but how will you federalize the car to get it into the USA? I didn't see any location in your profile, but if you're in the states I don't think it's that easy to get cars under 25 years old into here. If you know a way, please share by all means!