Without having read all of the replies:
If all of your other teeth are in good shape have the root canal.
If you're fighting a losing battle, pull the thing and find your way to dentures fastened "permanently" via implants.
Dentists want to "save your teeth" no matter what the cost and in the days of slippery wooden dentures this was a good advice, but now, they can can give you a good set of immovable (for 15-20 years) choppers at far less of the cost to heroically attempt to save each and every one of your rotten teeth.
You can spend $50,000 on saving your teeth and still have pain and no satisfaction.
Dentists, by and large, are quacks.
Go for the cheapest fix if the problem is major.