Originally Posted by Iride01

When stuff wears out on old bikes, it might be better to put new stuff on them. You probably won't find the exact same model and series part new anymore for a 2001 bike. And 105, Ultegra, DuraAce today won't be a direct exchange for 105, Ultegra or DuraAce of then.

It's better to know what your frame is capable of having put on it. Essentially you need to know the dropout and fork end spacing, and the BB shell width and inside diameter and threading if it's threaded. A few other things, but those don't get replaced as often.

Then you can find all sorts of new modern stuff to put on it depending on your budget.