Timing belt - dealer quote in Chicago area US$375 without water pump or tensioner - I did it myself - easy using instructions posted on Bay13. Interference engine - damaged if belt breaks unexpectedly.

Blower motor - much easier in 850 vs earlier models. DIY - again see Bay13.

5-speed very rare in US.

A/C evaporator leaks common (I've heard 30% incidence). Dash has to be removed. I did it at home but VERY time consuming and you can't drive the car meanwhile. Many other brands of car also require dash removal for evaporator and/or heater core repairs, so nothing special there.

Trim pieces, electrical contacts, relays and other little items may occasionally get loose, fall apart, glitch or quit - not due to corrosion, though.

Important to maintain crankcase vent (PCV) or rebreathing system to limit the chance of blowing out oil seals.

I don't know if others would agree but my 850 has been one of the easiest cars if not the easiest car to keep up I've ever had. Total out of pocket per mile driven or per year owned has been lower than typical or average values often seen. Dealer maintenance would make all that advantage disappear in a hurry. People on this website will help you with most all of the potential difficulties.