2005 Toyota Sienna Question: Estimate cost to repair or replace 2 head gaskets

Radiator replaced 2 months ago due to overheating - no prior indication and all in 1 day it happened. This week - cold outdoor temps - it was idling high 1 day, still no gauges indicating any problems, then white smoke the next and overheated by the time it got to the shop 7 miles away. Looks like 1 cracked block, possibly 2, but they say need to do both for proper repair. Won't know which until it gets to machine shop. My mechanic say Probably happened when radiator had to be replaced and just took a while to bear it's ugly little broken head!! Thanks for any help/advice and estimated cost.