smell antifreeze inside truck and windshield fogs up when heater is on.....

yes and yes it is a few hundred to replace because the dash on most vehicles has to be removed to access heater core

Odds are it is your heater core.

i to have a 95 f150 with the 4.9 inline 6 and my heater core is under the hood mounted to the firewall behind the ac evap canister, my heater core blew up, and a new core is only 25 bucks...