1998 Chevy S-10 REMOVING HVAC MODULE

I am trying to remove my HVAC module to replace my heater core. I have already removed the dash and removed the bolt inside the blower motor resistor hole. Apparently there are 3 stud bolts running through firewall from engine side holding the HVAC module on. The top one at center of firewall is no problem. The two on bottom appear to be a nightmare to access. Not knowing anything about this, there appears to be 3 possibilities to access these 2 lower stud bolts: 1) remove black plastic shroud on engine side that holds blower; 2) pull front passenger tire and fender well; 3) drop exhaust from manifold and come up from bottom. Any suggestions on the best way to tackle this problem?