The 8 round mags are like $50 a piece (when you can find them). I've heard that 8 rounds are the limit that BATF will allow for import, the higher cap mags have been classified as 'destructive devices' (whatever that means).
K-VAR has stocks which will fit Saigas - I'd think butt stock and pistol grip would be about $60, based on how much similar parts cost on my AK. I've seen the cheap Romanian side folders used.
If you convert it to pistol grip configuration, you have to do a 922r conversion - get a US made butt stock and pistol grip and a G2 fire control group. I've heard that 4 compliance parts are needed, so you could add the Romanian side folder, but check it out yourself.
Go to the 'Russian' forum in the AK section. A guy named 'Tomac' has a few posts which should answer alot of your questions.
As you can tell, I'm considering a purchase of one myself.