When buying a used ThinkPad, remember to check that the BIOS is not locked with a supervisor's password and that Computrace is not enabled and activated.
When buying a new ThinkPad, consider taking the IPS screen option if possible, as it doesn't cost much. Not only will it have better brightness, colour, contrast and viewing angles - you will most probably more than make up the investment when selling it. Corporate bulk purchasers don't usually go for it. (Comparison video)
The only tools you need for servicing a ThinkPad are a set of small screwdrivers and a nylon spudger (for taking the screen and keyboard bezels off), and possibly a pair of tweezers. A can of compressed air may be useful too, and a bottle of isopropyl alcohol and cotton buds are good for cleaning, but not on the screen. Never use nail polish remover (acetone).
When reinstalling Windows, try the Lenovo disc images, as longer battery times have been reported, probably due to custom drivers.