Other than pulling the engine how do you get to the spark plugs on the back of the 3800 engine in a 97 Park Ave? I can't get between the firewall to get to them. Any help appreciated.

On my 94 PA, it's tight but do-able.
I am also unsure if the 97 PA is significanly different from a 94 PA version.
To get hand room to the rear plugs, I had to remove a steel reinforcing bar that connects the two struct towers.

It is all in the tools you use. You need some short extensions and universal built into the plug socket, as well as flexible arms and hands. Heck. I change them all the time without removing the strut brace!