Is there a danger of breaking the exhaust, transmission or something else?
YES
You have to support the motor on floor jacks. If the motor drops you have a
real problem.

Does the computer need to be reset after changing the plugs?  NO

If you have any doubt about changing the spark plugs on your car you should
leave it to a automechanic. For the $100 or so its going to cost you, its
cheap insurance to leave it to someone who knows what they are doing. If
they muck it up they are on the hook for any damages
If you cannot touch it, reach it,  see it or don't know how to do it, leave
it, for a Tech.

In my 99 Monte Carlo Z34 I'm attempting to change the spark plugs.

I found out (as someone mentioned in here) that you do indeed roll the
engine. What you do is remove the engine mounts and insert a pully which
you can pull the motor 4 inches foward. My two questions are:

Thanks