super noober - Im not going to dump a ton of cash into it cause they only sell for $800-1400 here locally so doing say a $600-1000 engine makes no sense

That being said, since I have to replace these parts anyway I dont see why I shouldnt replace everything with upgraded parts since the labor is a wash either way.
Well you'd think it wouldn't make any sense, but if you bought that $1400 Blaster what would you have? Pretty much what you just had last week. You know:
"Drrrrraaaa-daaaa-daaaa",,, "Hey, there go the big boys! wonder where they are going????"..."Draaa-daaa-daaaa"
So, with a little work and a few bits from the speed shop:
"BRAAAAAP-PAAAAAP!-ping, ping, ping-(hard braking)-BRAAAAAP!"
"Holy sh*te! Look at that Blaster go! See if we can catch it..."
Priceless
How high can the compression be run up on one of these engines before one has to start using gas thats better than 91 octane pump?
About 150-160psi to maybe 180 if you had a better cut head.
Any point in doing any work to the cylinder head, other than possibly a slight shave to raise compression?
All the point in the world in my books. I have this (seen here to be odd) view that high compression and advanced timing are counterproductive to top rpm power and reliability in a two stroke, but they do fatten up the mid-range a bit. The Blaster combustion chamber shape is so bad, almost anything you do to it will make it work better. You want the flat area of the chamber closer to the piston (about 1mm) but not too much compression, which works out good, because a larger combustion bowl will make more power.
Are there any other inexpensive parts that commonly fail that are worth replacing while its torn apart?
Clean the carb and the air cleaner, replace anything that looks bad, make sure all your bolts are loctited and tight, use a torque wrench, and always remember: too much of anything is a bad thing.
Is there a copy of the service manual available anywhere to download?
Thanks again for any advice
You got it already, hope you have fun.