Need a root canal and probably a crown at 21 years old - advice?

I'm 21 years old, have had a few dental issues over the years. When I was 19 I had to have a root canal on my first molar due to dentist not filling properly, and in Feb this tooth cracked and had to be extracted because the root canal failed. Now, the same tooth (upper first molar) on the other side of mouth is having similar issues and pain. Dentist has said if the pain persists I will need a root canal and probably a crown. Am a bit concerned as I'm only 21!!