2001 Mazda 626 shifter cable

I recently had transmission problem, where I went to put it in drive and it stayed in reverse. Took it to a mechanic and he said it was the shifter cable. No problem, I order the part he goes ahead and attempts to fix it. However after 3 hours he says he cannot fix it as the heater/ac unit is in the way of where the cable goes.

does this sound right? Is it simple to get around this?

he sent me to some one else to fix it.