Gary Anderson did very well with his bolt action rifle, especially considering he is left handed and used a right handed rifle.
I haven't been in any competition for a few years, but I've been thinking about getting active again for the last few years.

You didn't say what type of High Power competition you were considering. I'm guessing NRA/DCM. I still have my DCM M1. I had an M1A, but sold it.

I think you'll find most competitors use semi-autos. Find a M1 Garand, an M1A, or one of the semi-auto M-16 variants. Starting out, you can be competitive in your class with a stock rifle. As you get better, you can have the rifle accurized by one of the gunsmiths who specialize in this.
Depending where you live there may be matches close by so don't let the possibility of fuel, food, and lodging costs dissuade you. There are many smaller matches shot on reduced courses of 100 or 200 yards.
If you are already shooting, you probably already have earplugs or muffs. I used to buy disposable ear plugs by the
box. On the firing line I often used both earplugs and muffs together. I was one of the few to wear earplugs when working the pits. Now I wish I had done more to protect my hearing.