I replaced the oil pan gasket on my 1998 LeSabre about three weeks ago. I would assume the 97 Bonneville SE would be the same...
(I went in there to inspect for sludge and do general cleanout, as my oil always looked dark even right after a change, I had just done the LIM gaskets and wanted to get any particles out, and my oil pressure was dropping at times)
Apart from draining the oil of course, you have to:
1) Remove the plastic flywheel cover on the transaxle side of the oil pan (2 bolts, easy)
2) Unhook, loosen and pull part-way out the oil level sensor on the front-of-car side of the oil pan (large adjustable wrench, easy)
Otherwise, I had no parts obstructing pan removal; however...
Whatever hack shop monkey put the last oil pan gasket on used an entire 55 gallon drum of black RTV, fully and thickly coating both sides of the plastic gasket, so it took me about two hours to slowly and carefully cut away at the RTV with a razor blade, gingerly prying the whole time, to break the RTV loose enough to actually drop the pan without denting the heck out of it. It then took me about another hour to scrape away all the RTV on the pan, down the outsides of the pan, pooled a half inch deep inside the pan, all around the engine block mating surfaces, and running up the sides of the engine block.
I hope you don't run into the same kind of RTV problem I did...if the last pan gasket was installed right, dropping and replacing the pan is a 30 minute job. If like mine, possibly a 3-4 hour job. Be prepared.
While you're in there, change the gasket on the oil pickup tube (my FEL-PRO pan gasket kit came with one), and clean the pickup screen.
(In my case, the pickup screen was half blocked with the RTV earlier mentioned...this caused my oil pressure problem. I also had about 1/4 inch layer of sludge that I cleaned out).
I put a new FEL-PRO plastic pan gasket/baffle back on with no RTV at all, and it hasn't leaked a drop in three weeks.
2004 Buick Lesabre Limited, Gran Touring; Bone Stock
1998 Buick Lesabre Limited, Gran Touring; Mods: Poly sway bushings/endlinks, Tru-Cool trans cooler, Thrasher shift kit (med), PLIM, front PEM; Mods in progress: Alot of stuff, but slowly...