I have a few questions about adding a DEI remote starter and changing the head deck. First, is with the remote starter. Will the new DEI remotes work with the stock alarm/door locks/driver info center? If not, how do you set the alarm and door lock options like you do with the GM remotes, or do you lose these features when adding the DEI starter? The second question is, if I switch the Bose radio (CD & tape) with a new unit, how do I change the dash chime volume since I won't be able to do it with the #6 button any longer? Or should I just get better sounding speakers and leave the Bose unit in? Lastly, I bought a new set of replacement SoftTrim leather seat covers on eBay and was wondering if anyone ever took out all their seats and how long it would take for the swap? Thanks.........

Let me see here, such a long list and I had to search for your trim level (Se).
You have to get a VATS bypass for the autostart and I think there is module that will allow you to use the power locks.
For the head unit try here for some options; http://www.tune-town.com/Cars/stuff/...Bonneville.htm
TaylorD has the advise for high systems in a newer gen Bonne. Post for this in the audio forum maybe he'll drop by
I have removed both fronts seats in my car (to replace seat heaters) and can help out if you need. Removing them is straight forward once you disable the air bags. The back cushion though is tough because of the air bag and seatbelt mechanism.
Do you have side air bags?

Dug up some good info, check the audio forum will share with all.

Yes, I have the side airbags. I think the hardest part will be with the front in the seat seat belts. Do I need a special tool for the headrest'*?

Slide a small pointed tool into the headrest retainers (I used a piece of coat hanger) to release the spring clips and pull up on the head rest to remove.
To remove the head rest peg pockets(?) you have to have the cover off, and reach into the cushion and pinch together the 2 spring clips, now pull up.
The seat belt is not too bad. Remove the plastic tower cover (it just clips on, pinch the sides to pop it open) and the rear bolt to free up the shoulder retractor. the lap seat belt reciever is a simple plastic cover and bolt.