Granny bought an '02 new, she's was close to 110K miles last time I drove it, a few months ago.
Religious 3K mile oil changes but other than that, no real maintenance.
She had to have the intake manifold gasket replaced about 2 years ago, I remember her gripping about paying $600 to fix it, and she "didn't even know what they did."
The TPMS light is always on, has been like that for 5 years or better.
The fuel sending unit died, gas gauge doesn't work, has been like that for about as long as the TPMS light has been on. She was quoted something to fix it, she can't remember how much, just that it was, "way too much when she can just reset the trip, and fill up every time she goes grocery shopping."
Currently has a CEL on for a coolant temp sensor, but I haven't gotten around too it, I don't make it over there as much as I should, and I had forgotten it until you posted this thread.
The Century is a fine appliance, Granny's has cloth interior with power driver seat, it's comfy, not Volvo comfy, but comfy, dual zone air, and a decent sound system with CD & tape deck.
Husky makes decent, direct fit floor liners for them too, that was part of Granny's Christmas present last year.
I've owned 2 GM 3100 (different from the older 3.1L) Grand Prix, one made it near 200K miles, the other made it closer to 260K miles. The second '94 Grand Prix got a junk yard engine with less miles swapped in for less money than the cost to replace the intake manifold gasket, but a guy owed us a favor, and has a bit of a personal junk yard. YMMV.