"Yesterday afternoon while driving my 96 Sephia 1.8L, the radio started
cutting out, actually going on and off (intermittent power out). When
I turned off the a/c, the radio would come back on and stay on, when
I'd turn the a/c back on, the radio would go off. Otherwise, it
seemed
to be running fine. But it just seemed like there wasn't really
enough
electricity to run everything properly...lights seemed a little dim,
wipers seemed extra slow. "

It's either a bad battery with a shorted cell or a problem with the
charging system(i.e. bad alternator, regulator, wiring problem, massive
short draining the system, etc). You need to read the voltage at the
battery and see if it is charged(12.6-13.0 volts with the key OFF),
monitor during cranking(if it drops to something rediculous like 8
volts, you have a bad/dead battery), and then monitor with the engine
running. You should see 13.6-14.0 volts at idle with the engine running
and all accessories OFF if the alternator is doing its job. If it stays
down around 12.5 it means the alternator is not charging. You could
conduct all of the above test with a cheapie voltmeter from radio
shack.

On the 96 sephia the alternator is held in by two bolts, both are
accessable from the top but getting the alternator out would probably
be best done from underneath. I have a 97, and I've never replaced mine
but had it loosened/out of the way for a timing belt job and it looks
like it would hit the intake manifold/AC hoses if you try to pull it
out from the top. If you have to replace it I'd suggest disconnecting
the battery, loosening the bottom bolt, removing the top bolt, removing
the two electrical connections from the alternator(2 wire plug and the
large 12v main connection) and then crawl underneath, remove the lower
bolt and remove the alt. It's definately a DIY job.

Good luck with it.

Chris