The heater core is hard to replace. The easiest way is to pull the dash. I've also heard of a few people changing the heater core by only pulling the dash cover but I've never done that way. Good luck...
The dash can be loosened and pried far enough to get clearance for box removal, BUT I'm not sure how much I would want to pry on a 30+year old piece of plastic that's almost irreplaceable. Thus I would remove the dash.
And having to remove the AC lines ... I get shivers just at the memory.
Plus, splitting the box sucks. Make sure you remove all screws and clips. Pry gently and work around the box evenly and carefully.
This is not a job you'll want to do twice so do it the absolute best you can.
And, who is amanda chaingete, looks like it could be the name of a S&M **** Actress.
I removed my core without too much trouble without removing the dash. My car does not have A/C though. It was a lot of arm scratching because of the tight areas that you have to work in.