I had one last summer. It was my own fault too. The last time I went to the dentist I pointed out what I thought was a cavity, and he said, "well, it's just a decalcified area for now. Let me know if it changes." I then did not go to the dentist for almost two years, and when I finally made it back it had turned into a bigass cavity.

The first appointment, they drilled away a lot of the tooth, pulled out the nerve, and filled it all up with a temp filling. The next time they fitted me for a crown since a lot of the tooth had to be taken away for the root canal, and put on a temporary plastic crown until the porcelain one came in from the lab. Went back in for them to put the porcelain crown on which was a pretty quick appointment.

Overall the experience was pretty pain-free. This was the first time I had any serious dental work done while awake. Previously I had gotten teeth pulled 4 at a time (once to make room for braces to work, and once to get rid of impacted wisdom teeth, both pretty common) and got knocked out for the duration. The root canal, just with a good amount of novocaine, was fine. The only "pain" was that my head felt numb for a few hours while I waited for the novocaine to wear off. But yeah, since the nerve is gone you can't really feel much of anything.

Now I have a porcelain crown that makes up pretty much the whole top of the tooth and for all intents and purposes it acts like a real tooth.