I was in the same situation as you, mild dyskariosis and hpv, and I was a bit concerned beforehand about what to expect! The actual colposcopy is much like a smear, except for me I was sitting in a chair with stirrups rather than lying on the bed in the doctors surgery!
They put the speculum inside you as they would do a smear and then set up the microscope so they can see your cervix clearly.. They wipe your cervix with a sort of acid solution, it doesn't hurt really but it felt a little cold for me!
Then your doctor will make a decision on what to do next based on the level of abnormal cells they see (they show up white on your cervix when the solution is applied). For me, although the doctor had said she'd probably take one look at me and tell me to come back in six months, this wasn't the case, there were more abnormal cells than she was expecting to see, so she took two biopsies. (Most of the time, I don't think the doctor knows if they are going to take biopsies until they're 'in there'. If you prepare yourself for having a biospy and don't need it hopefully that will be a relief for you!)
The biopsies were over really quickly (she didn't really give me very much time to even process what was happening - which was maybe a good thing!) and they only way I can describe them was that it was like a pinch?! She did warn me not to watch this part on the screen, I had been watching intently up until that point! After the biopsies they put a silver nitrate solution on your cervix to stop the bleeding as much as they can.. That felt a bit weird. Kind of like when you have a papercut and you get something like lemon juice in it! Bit strange but not exactly excruitiating.
I felt a bit sick afterwards, but this might be a combination of it being lunchtime and being a little bit in shock at the surprise biopsies! I did go back to work though for the afternoon, I work on a desk job so not a strenuous job to return to.
If you're super sensitive to pain, and wanted to err on the side of caution I guess you could always take a painkiller beforehand? Honestly though, it'll be over before you know it. Are you taking anyone with you? I wish I had, they usually let someone sit in and hold your hand (at least they did at my hospital, I wish I'd known that before the colposcopy!)
Good luck, thinking of you and sending positive thoughts over.. Let us know how you get on :) xx