I had my first surgery when I was 24 and I was scared out of my mind! But, honestly, your image of it is a lot worse than it actually is (or at least that was true in my case lol). They take you into the operating room and the anesthesiologist talks to you bit and may ask you a few questions and then... you wake up in recovery.
I'm 32 right now and have had surgery 3 times (gallbladder removed, brain surgery, weight loss surgery. In that order lol). I was only scared the first time because it's the unknown that terrifies. And yeah, you'll be in pain when you wake up, it's typical of any surgery. But, you tell the doctor and they'll give you some lovely pain meds and you should pretty much be fine after that. Just make sure you walk, walk, walk, because you want to get that gas out of you and that's the only way to do that. Yes, it'll suck and you'll be sore and won't want to do it, but you actually feel a lot better when you push yourself a little bit. Not too much, just a little. If you're have the sleeve surgery (or DS or Loop DS) then your incision site where they removed your stomach is going to hurt the most. I had to have my mom help me in the shower because if I moved a certain way it hurt so bad I'd start crying. Also, getting up hurt. And sometimes sitting down. However, I also didn't take my pain meds so I'm not really a point of reference lol. I have a high pain tolerance due to my TN and I hate how pain meds make me feel so if I feel like I can withstand the pain I do and won't take the meds (I had a 30 pill prescription. I took maybe 8 or 9 pills of that and still have the majority of the prescription left over somewhere...).
So yeah, it's nowhere near as bad as your mind is making it seem. Just focus on how you're going to feel a year from now when you've lost a ton of weight and are a healthier you! I wish you the best!