What is the best way to get all my tires changed?

[KausalityKid]

My 41 foot 2019 380TH Montana high country has six tires, three on either side although all the manufacturers pictures and description say it’s only a two axle model with 4 tires. I am a newbie in this is my first RV so I don’t know what I don’t know. I have taken it out five times of distances no more than 2 Hour drives and have had blowouts twice. The first blow out was a freakish accident. The second one I have no idea. I want to swap all six tires and two spares for 12 ply new tires. I don’t want to go to a dealer because I know I will pay a premium for the tires. I was thinking of changing them all myself, but that task is to daunting. Removing all six and the one blowout spare that I have, Plus finding a rim for the second spare that I want, taking them to the tire shop and getting them replaced, then mounting them all back on it seems probably too much of a job for me alone.

Any suggestions on where to buy the tires at the best price?
Any suggestions on how to get them all swapped out?