I replaced the o-rings in mine. Search the archives and you will find the sizes of o-rings needed and if you can find them locally it may save you a few bucks. The rebuild part is easy compared to the dismantling part, because the master cylinder has to come off first. I used this opportunity to drain the power steering fluid and replace the filter. As long as you are bleeding the brakes anyway its a good time to flush out all the old brake fluid too. Be sure to use DOT 4.