Has anyone used a doula during delivery? Did it make a difference? Was it helpful? Did your insurance help with the cost? Do you have any advice when looking for a doula?

I'm trying for a VBAC this time (2nd baby), and I was thinking of using a doula. My first labor went the complete opposite of what I wanted and ended in an emergency c-section. I'm hoping that a doula might be able to help me through labor and help me stay on track with my birth plan (as much as is possible) and hopefully avoid another c-section.