will distortion hurt my amp?

Nope.

Might damage your ears if you play it too loud, though.

 

it will only hurt your speakers if you play the amp so loud that the amp adds its own distortion on top of the intentional distortion.

Know the limits of the amp and cab (volume settings that cause it to distort) then play with your pedal.

If I'm playing really loud I set my guitar max, effects to just before distorting amp on loud notes and then the amp/preamp volume to just before distortion, then use my guitar volume during gig. I hate to turn around too much to adjust, especially during performance.

under those settings when you click in the pedal circuit make sure the volume doesn't jump way up when its switched in, this will run the risk of unhealthy distortion. o.k., I just thought of something. most pedals like to get a strong guitar signal to work properly, so use your preamp volume to lower volume to useable level under the previous settings instead of the guitar.

I think this is right?

 

No, wear earplugs though... I was going to say it most likely will if you clip your amp, but I think it would be kind of hard to clip 1000 watts

 

It can be done

Actually most distortion pedals deliberately clip the signal to achieve the effect. The difference being that when a power amp clips, it's deliverng more than it's rated output power. When the distortion pedal clips, the amp, in theory, is still operating well within it's limits. Therefore nothing gets damaged.

If the amp has a clip light, keep an eye on it. the general consensus is that the occasional flash is OK. any more than that and you're running the risk of hurting your speakers.