If you can't be bothered to do a search for "MPC 2500 pad replacement" then you probably aren't competent enough to do it yourself...
I can't view this video at work but I'm assuming its what your looking for judging by the title and a .3 second search using google.com
(YouTube - Akai MPC 2500 Casing Removal & Pad Install MPCstuff.com)
http://www.youtube.com/watch?v=RhYqySGH-7k