First thing is to get something to monitor your engine and see what condition it is is. I suggest one of the Edge Insight monitors. If your ECT and EOT look good flush the cooling system with VC-9 and Restore the refill with an ELC CAT EC-1 rated coolant. If you can delete the egr setup, if not install a Bulletproof egr cooler. Then drive it. If you get the Ford Gold coolant out and delete the egr cooler or install the Bulletproof one the chances are good you won't need to do the head studs. If for some reason you do have to change head gaskets do the studs then, but switching to ELC and taking care of the egr you have removed the major source of blown head gaskets.
Just realized that you also posted about a sweet smell. You need to do some troubleshooting. The links in my sig have some good info.