Thank you for the tips, I really appreciate it. I ran into a lot of problems with cheek weld on the factory M1A stock, so I decided to switched to VLTOR stock. It's seem to be better but not completely. It's super hard to get a good cheek weld and focus. If I get a set of lower scope rings then my scope with hit the rear sight

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Getting the scope lower will likely still not produce a stockweld where the complete weight of your head is resting on the stock, allowing for the eyeball to be squared with the eyepiece. Since you must have a proper stockweld you will need to build up the comb in some manner, or purchase a stock with an adjustable comb. The other option is to remove the scope and use the irons. If you are a novice shooter, irons may better serve marksmanship development.
Also, since long range shooting is what you want to do with your M1A you may want to try out NRA governed LR competition, selecting to shoot in Service Rifle division, which is the only division where you would be competitive with such a rifle. This competition will require you to use an "as issued" type stock, as well as iron sights.
You may have no interest in this sort of competition; yet, taking the plunge will promote learning for everything important to good shooting, which is what you said you want to learn.
Since just showing up at a LR tournament may be somewhat intimidating, after all right now you don't know anything about it, you should contact the CMP for a list of Clubs in your area which will be hosting M1 Garand Clinics in the immediate future. Attending one of these will give you a good basis of understanding for how to do it. Take a friend with you to make it even more fun.
One more thing, this is usually the point where the "shooter" responds to my suggestions by saying something like, "well, I already know how to shoot", or "I'm not interested in competition". Before you say that, think of all the fun you'll be missing, as well as missing an opportunity to actually use a venue manufactured explicitly to help folks like you learn how to it. Trying to learn it on your own is not going to get you far. How much can you learn from someone who knows nothing about it? Competition will introduce you to folks who indeed know how to do it and are willing to help you learn how to do it too.