no problem. See if the mechanic has any idea about the warning lights. Other than that, for a car of that year, that mileage is SUPER LOW!! My '99 had a few more miles on it when I got it last year. Their price definately seems reasonable, unless, like you said, there's some costly brake work needing done.
I'm glad to hear it has the 3.1L engine as opposed to the 3.4. Although the 3.4 is faster, its probably not worth the hassle of trying to repair it (from what I've learned on this forum). Like I said earlier, if they're properly maintained, the 3.1 will get relatively high on the odometer. Because the car in question has such low mileage, I would buy it (if I was in the market for a 3rd lumina..hahaha). I imagine someone else would do the same, I imagine that car won't be "for sale" for long.
As far as those links go, I believe there were about 60+% who said they would buy a lumina again...meaning 40 or so % wouldn't ....however, that thread encompasses all luminas (from the 90's until they stopped making them in 2001, it also includes the lumina APV and all the different engines that were availiable including the 3.4 and others) Plus you've got to take into consideration that not everyone treats their cars well. If you take car of it, it will take care of you

. but not everyone thinks like that.
Those cars were very popular so parts are relatively easy to find. Most of the parts are reasonably priced, however some can become costly, but you'll have that with almost any make/model. Also forgot to mention that insurance is good on luminas as well and that's a plus with the rising cost of....EVERYTHING these days. Good luck, I hope the brake llights aren't a big deal and that everything works out for you!!!