Sure it's easy just remove the front and rear half of the car and there is your heater core.
It's actually not that hard just move the seats back and lean them all the way back, Expect to spend some time on your back streatched out in the seats and at the chiropractor later.
You don't have to remove the steering wheel or disconnect the steering shaft, just stretch the dash gently after it is as unbolted as far as you can get it. I had some slight scratches on mine but it wasn't the worst.
If your heater core is plugged internally you can use compressed air to blow it out(in reverse direction) with limmited success, but mostly it is dirt, dead leaves, lent, and the occasianal dead rodent impeading air flow through the core. Or they are hard plugged.
When taking apart the air box (on a bench) it is easiest to put a flat blade screw driver on the outside of the horseshoe shaped clips and twist as aposed to prying, be carefull when reinstalling as they tend to bite at fingers.
Good luck and do it when it's warm instead of waiting 'till late november in an open car port with an electric space heater in the back seat.
NMc