I don't know if all 700 series have Auto Climate Control. Mine does.
I think it adds complexity (hours of labor) to the job.
Total PITA to replace the core. I considered doing it myself, but quickly changed my mind after looking at what's involved.
I was quoted $900- $1000 by several shops until I found a S&M Volvo mechanic who agreed to do it for only (!) $500. I provided the parts (heater core, heater valve, both hoses). Buy parts on the internet- shop around from the recommended vendors on this list and save $$$.
I recommend using someone who has done the job before and is experienced with Volvo.

$700 is a fair price for this area, *IF* it includes all parts.
If not, keep shopping!
Do it Soon, the problem can quickly turn into a full on steam bath/sauna and no amount of wiping will keep the windows clear. An inside wiper from the 200 series might do the trick until you can afford replacing the core. Look in the archives. ;-))