Here's what I'll tell you. Will there be a sharp learning curve? Yes. Will it possibly not be what you thought it would be? Yes. Finally, will there be other guys going through that have multiple combat deployments? Yes. Does any of that matter? Not really. It all depends on you.
First understand what your asking for. Being that your coming from the support side I'm guessing that the extent of your suck factor isn't too much higher than boot camp or MCT, nothing wrong with that. However, realize that A&S and ITC will take you way beyond your current comfort zone. It will suck hard. Then realize that if you make it to a team things can suck even more, only difference is that now its too late to quite and doing so will probably cost somebody their life. All this stuff looks cool on the recruiting commercials and movies until your the one freezing your ass off on some mountain for three days, or pen'd down by machine gun fire praying that the CAS drops before you get smoked. Let's not forget the work schedule, which in short will keep you busy the majority of the year, and I don't mean nine to five. Not trying to scare you off just want you to realize the magnitude of what your asking for. Its very rewarding, can be really bad ass at times, but also requires a lot of commitment sacrafice and can be dangerous as hell.
Second, if your still dead balls set on doing it don't worry about your competition. Your goal is to go out there and impress the instructors at A&S. There is nothing at selection that will test your "combat" skills. If you go out there and perform you'll get selected and they will teach you everything you need to know to get the job done. Like I said I'm not going to lie its going to suck for you, only because right now your brain already has a barrier set for what you consider hard. Once you break that barrier and establish a new one you'll be amazed at what you can do, but it will take some time and it may not happen until after you graduate ITC, if you graduate. The only limit is your mind.
So it can go one of two ways. You can be one of the seemingly hundreds of Marines I run into who give me there quick "well, I was going to join MARSOC or Recon, but (insert excuse here)", or you will contact a recruiter get the information and take the next step. Either way the balls in your court.