Glad you did your tune up. Your car will almost always thank you.
A couple things for future reference. Keep a good eye on the Bosch plugs as the Bonnevilles often do not like them too much. Many here have had issues with them after a short time. Not everyone though, so just keep a good eye on your mileage and performance.
Also, The NGK55s can be had for probably the same or less than Bosch plugs.
Regarding the SES light. If it doesn't go away very soon, have it read at your local AutoZone or Advance. They will usually read the code for free. If you do, make sure you write down the code number and any other info you can get and post it here.
Just as a quick check, look in there and make sure that the #6 plug wire is not too near or touching the O2 sensor or it'* wire. That can sometimes throw a code.
Again, glad you are looking after your car. you will never regret doing regular maintenance.
Mike: 1997 SE w/ 183K, aka White Horse
, Gutted Airbox w/K&N, drilled 180* t-stat, tint all around, clear corners w/SilverStars, "PONTIAC" light up tail, PEMs, NGK TR55s