'95 DeVille Tune-Up

I just inherited a '95 De Ville from my mother, she bought a hybrid! She kept up with the oil changes and has had regular service as far as I can tell from the receipts. She replaced the factory struts with passive ones so I get the "Service Ride Control" message, but that doesn't bother me. But I don't think it's had a tune up recently. It's nearing 125,000 miles and idles a little rough and misses when accellerating, especially when cold.

I'd like to do a tune up myself: plugs, wires, coil pack, air and oil filter, PCV valve and oil change.

What I'd like to know is:

1. Can I get to the back plugs by removing the engine cowl and if so is it difficult to remove?

2. Does anyone know what regularly scheduled maintenance is due around 125,000 miles? I'm especially interested in when a new timing belt (chain?) is required.

3. Did I miss anything on my tune-up list?

Thanks