CPAP, Exercise, and Fatigue

Hello, the VA is delivering my first CPAP machine next Tuesday. I've been reading about it but still had some specific questions I couldn't find solid info for. From what I've seen my stats matter, so here's what the sleep study found:

AHI: 129.9

O2 NADIR: 77%

I don't really understand what that means but my doctor said it wasn't good. I've been tired since 2009 but always assumed it was because of nightmares. For other people in similar situations, how long did it take before you stopped being perpetually tired? I've heard the masks are uncomfortable, how does it compare to a gas mask? For people who exercise regularly, how did it impact your strength? I've read that it'll increase my strength but I'm curious how impactful it really is.

Lastly, if anyone has tips or advice for a newbie, or any extra things I can buy before it gets here in preparation, I'd greatly appreciate it. Thank you.