Because clones are inconsistent, you might be able to replace everything easily or it might be a bitch. I've had both from jg. Luckily the ones I own were easy. There's no definitive answer here, it will vary individually for each clone gun. But they are getting better.
Unless you have the experience and patience, you're better off just buying better stuff or buying a complete box.
Grand Poobah of T.W.A.T.