My wife got me my saiga for christmas. I just ordered/received a tapco T-6 stock. That's the only modification I've done to the weapon. That and adding a 30 round surefire magazine to it. (These 2 items made it 922r legal; which while not my concern; is one less headache). With the stock the way it is; I have no problem with the trigger assembly. (No reason to change it). I like the original foregrip. (No reason to change it). I do have a scope rail "Weaver-Picatinny" on order, along with a reflex sight. That will be pretty cool. Other than that, I really don't plan on converting anything. I don't really see a need for it. Anyway, for those who want to make the most basic change to their Saiga; which usually means a 30 round magazine and a pistol grip; you can get the tapco stock/grip for about $45. You can get American magazines for $11-$40. So no; you don't have to spend hundreds of dollars to make the rifle the way you like it. You can go as cheap or expensive as you'd like.
Just got my reflex sight in today, as well as my mount bracket and my laser. I still need to sight it all in; probably this weekend. But it's about where I want it.