i was also so nervous about this - i had one done earlier in july.
are you being referred to a gastro/specialist? or is your gp just sending you for the scope on its own?
i was really nervous about it and refused to go through with it for a long time. i was like you the only thing i was worried about was the gagging - i just cant stand it.
i actually asked if there was in anyway possible for me to have it done under some stronger sedation/anesthetic [they do it for small children, while totally asleep - so my mum said if they could do it small children then why can't they do it for me?] so i asked if this was possible and luckily thats how i had it done! it was done with an anesthetist, but it wasn't like a "propper" anesthetic. the anesthetist said it's enough to make you go to sleep, and ensure your totally asleep for the procedure, however not enough to need to be tubed or anything [he says very occasionally can someone drift so deep that they do need extra help, but even if they do - its not a problem]. i had some oxygen to help me breath, on my own while the procedure was carried out and they put me on various monitors. i was totally asleep and i didn't feel a single thing. when i woke up i didn't feel like anything had happened. nothing hurt and i felt like i'd just woken up from a normal sleep tbh. i was coherant and knew exactly what was going on as soon as i opened my eyes and was able to go home [feeling no different to usual] within 3 hours [although i was quite ready to go within about 2 and was dressed and just sat in my room waiting]. the next day i went out and about with friends and carried on like normal.
the only ill effects i suffered were that i was a bit dizzy at first and had to sit up very gradually over the first hour before i came completely sat up, i was cold, and for the next few days i had a very very slight sore throat.
thats it. i couldnt say what the procedure is like under normal sedation - i was too scared to risk it. but if it would make you feel better then theres no harm in asking if you could have something stronger?
good luck! let us know how you go