If I send a reseed request, will I get a notification alerting me that someone has started to reseed or do I have to keep checking the video I want reseeded to know?

You won't get a notification.

Should I download the dead torrent anyways, so once it's reseeded I can automatically leech it?

That's what I do. In my experience a torrent comes back to life after a reseed request about 10% of the time. I"ll make an initial request, and then perhaps another request a few days later, another a few weeks later, and then give up.

Making requests too often is annoying to other users. I'll get requests from time to time for material I've deleted, and that's not a problem...but to get a request for the same stuff over and over again is tiresome.