Newbie: New Tires and Sailun Brand Tires?

[Mosnowman]

I have researched through all the threads, and think I have reached tire brain over load. There is so much great advice from you experts. In any event here is my situation.

I have a 2018 3721rl Montana - 39' 7" - Dry Weight 13,317 lbs

It has been sitting stationary at my lake property on a cement slab for the past 4 years. We have never traveled with it. Factory tires. I am retiring, and now we are planning to start traveling with it. I have read the nightmares on here regarding blow outs on factory tires and it seems the consensus agree that Sailun Tires are the way to go. So I have a few questions.

1. If my Montana is sitting stationary for 4 years the factory tires are probably best replaced before traveling on them?

2. What size of Sailun tires would you replace them with?

3. Is there a best place to buy them? Price?

Thank you for any help. I know we newbies can test your patience, but I am trying to learn as much as possible before going on our maiden voyage.