The Herman Miller Aeron chair is one of our favourite office chairs, but it's an expensive piece of gear. If you can snag a second-hand one, weblog Apartment Therapy has a full guide for refurbishing it yourself.
You don't need much to refurbish an Aeron: just a few Allen keys and a spanner. Once you disassemble the chair, you can track down replacement parts cheaply from companies such as Office Designs, and then easily refurbish it yourself. One of the great things about the Aeron is that everything is user-serviceable, so it's not nearly as complicated as you think. Head over to Apartment Therapy for the full guide.
How to Refurbish a Herman Miller Aeron Task Chair [Apartment Therapy]