You will not find a 10 year old one...first was 2006. If you get the 3.8 engine, take care of it and it will last and last. I have read that that 8 cylinder NorthStar is not good. Leaks oil, mechanically not a great engine. In 08 they replaced the 3.8 will a smaller 6...I have heard nothing bad about them. From what I read on the other Buick sites, some are Lucernes full of problems, and some, like mine are problem free. That said, I bought mine new in 06 and it was a mess right off the lot. Everything was fixed under warranty, so anything you buy should be fine in that respect. Some items to note:
Front Wheel bearings were an issue on some cars. I have had one replaced
OEM factory chrome wheels were garbage...chrome peeled off resulting in leaking tires.
More recently people are reporting inoperable rear doors.
Door handles are plastic and break especially if you yank of the doors.
Other than that, it really is a nice vehicle. When you buy second hand, you take your chances, but on a good note, people that normally drive Lucernes are not drag racing them, and so probably are reasonably taken care of. Good luck.