Did I go too Far?

I'm an IT guy also, and I know exactly how this happens. Us IT guys get very comfortable in our jobs and start slacking off a lot if we aren't motivated. This is probably what happened and the guy just kept putting you off over and over. The best thing to do is to raise hell with their manager and he will surely get a fire lit under your tech. I probably wouldn't have been happy with you changing out the power supply, but it could have been worse.