To tell you the truth, I never met anyone who wanted to be a sniper from the get go.  The sniper's in my day kind of fell into it because first they were recognized as an outstanding shot and then recruited.  

The whole sniper glamour image is a recent thing brought on by the media. They had all of our respect due to how hard the duty was. The duty it's self is very hard with long extended periods of being in the field.

Like the guys say, you have plenty of time to make up your mind.  One way to help, would be for you to do primative camping trips for that's the life.  Living for days on what you can carry on your back, is the biggest part of it. You may find you love it and you may not.

Suggest you read the posts in the Survival Forum for ideas on gear and potential trips.

The service is like a world in it's self with jobs of all sorts.  Deciding what you want to be is difficult for experience will change that.  I thought I knew when I went in but did many things different after some training and experience.  

Getting a good idea now will help you in a couple years in making up your mind.

Tj  

You want to be a sniper?
Here is a quick test.  This winter, jump in a pool, then lay down.  Stay there all weekend and don't move.  Do it overwatching a freeway and count every blue BMW that comes by with three passengers.
After 48 hours, if you still want to be a sniper, you will be a good one.
How fast can you run?
That will determine, to a large degree, how much you will enjoy your experience in the high speed low drag units.
They call them high speed for a reason.
If you like it

Scout snipers lie in one spot and count trucks, gather intel, surveil targets and maybe for days on end, whizzing and pooing themselves where they lie sometimes. It's not a glamourous job all the time. Rarely, they may engage a target depending on the mission. You are not going to be whacking guys at 800 meters as a general rule of thumb. It's a job you have to have an incredible amount of patience to do as it is a job of very little action besides movement to a target, gathering info and movement from a target area.

Generally you have to make your bones on active duty for at least a few years first to get considered for a STA platoon. The sniper indoc, which is a few days long, is the tryout It consists of a Marine Corps PFT, land nav, PT, night land nav, PT, swim for time, and our unit did a 25 mile hump with full rucks which the STA platoon attached it's wannabe to after their three days of torment as the finisher.

The army direct to SF really isn't unless you meet all the requirements of the contract which can take years to do to actually make it to the tryout. No one goes direct.