Hey...I hope this isn't too late....I replaced a heater core in the fall, for the pros
it is an 8-12 hour job, as the dashboard must come out, et al.
So it is a pricy job, my car was/is mint, with just 104K at the time, so it was a worthwhile venture!
Are you sure the HC needs an update, as other issues may exist to cause a leak- ECR valve(?), et al...
Volvo core is $400...aftermarkets go $125ish...why not?!?
Check out www.brickboard.com as well fo mo info bro
mike