Tech, I expect to keep my 1997 850 for another 10 years. I still drive a 1984 Nissan Maxima and 1985 Mitsubishi Starion -- both over 200K miles. How frequently have you replaced...

A) Heater Core.

B) Heater hoses on engine side of firewall.

C) Are there any heater hoses on passenger side of firewall?

D) Heater hose plastic coupler (secures O-rings in place)
http://www.fcpgroton.com/volvo850cooling.htm

http://www.fcpgroton.com/images/3522035sm.jpg
Genuine Volvo
3522035
Hose Plugger (Coupling) The heater hoses connect to this part fits both Turbo and Non Turbo Models
$36.00

Also, the driver's side sunvisor will not stay up. I am planning to replace soon. I have heard that the electrical connector for vanity light is buried underneath of the dash. Would it be a good idea to replace sunvisor while replacing AC Evaporator?

 

Yes replace while the Dash is out.
Heater hoses not all that much.
Heater core I would do to be safe.
The Block don't worry about but I would buy the o-ring kit and update them.
You may have to get from Dealer though.
No hoses on the right side.
Only the 2 that go into the Block you posted the Pic of.

 

Tech's Evaporator Procedures...
https://volvoforums.com/m_7364/tm.htm

ichrolle's Evaporator Pictures...
http://people.umass.edu/gfeldman/vol...vap/index.html

 

Did you do it yet?

If so did it com out ok?