Um... yeah.... you absolutely need to take of the harmonic balancer in order to get the front cover off the motor. It is physically impossible to do it any other way.
As far as that bolt is concerned, give it a dousing with a good penetrating oil at regular intervals. Allow that stuff to really work into the bolt/threads. After many years and many miles, those things can be absolutely TERRIBLE to remove. Like the other guys said, use a long breaker bar with some kind of cheater bar on the end. If you really fight it, you'll be able to get it.
Do you or someone helping you have some experience with a cam swap already? I'm not saying you're incapable of doing it, but it sounds like you don't have a lot of confidence in finishing this job. Make sure you hit the details, like prelubing the cam and lifters, packing the oil pump full of Vaseline, and using Loctite and/or RTV on the appropriate nuts and bolts. Make damn sure you've got the thing timed right when you reassemble, and follow any break-in procedures that came with the cam.
1997 SE w/SLE package
"White curse? I think it'* more like.... WHITE FURY!" - MyLittleBlackBird