Nice choice of laptop! If it’s still working alright, you’ll probably be able to use it for some time to come (my iBook Dual USB G3/500 still works like a charm, even if it’s a bit challenged capacity wise). That kind of service might end up costing you a pretty penny, so you may be better off reading up on how to keep a clean system, avoid filling up your HD with unnecessary things, etc. An archive and install from time to time (ensuring you back all vitals up first, of course) is a good way to keep your system from getting bogged down. Also, depending on how much RAM you have, you may want to go easy on the OS upgrades – if you have an OS running on it that it comfortably handles, might be an idea to stick with that.