Is there a diagram for the 2000 Toyota Camry's engine?

Yes, there is a diagram for the 2000 Toyota Camry, and You can access it directly on Toyota's Service Blog here: https://www.Toyotaguru.us/camry-repair/camry-electrical-wiring-diagram.html. Given that You're driving an older vehicle, I'm assuming You're well and good out of warranty, so I'l not give the usual cautions about violating that. I will, however, remind You to disconnect the battery before You do any electrical work under the hood: live wires and lots of metal can turn into a pretty bad day if You're not careful.