I have a 2001 Chevrolet Impala LS that I purchased new. At 40, 000 miles of easy driving. The transmission went out and cost $3, 000 to replace.
I did NOT go with a GM remanufactured transmission.
There were no updates from GM to upgrade the weak internals for this transmission which has had known weaknesses for years.
My advice is to not buy a Chevrolet Impala. GM won't give you any grace if your transmission fails after the warranty period and there are too many people having problems with these transmissions to take your chances with one.