I understand, but now my major concern is, what if I hurt her on our wedding night. Well, we'll just have to make sure you don't hurt her :)
"what if she wont want to anymore after that" It is possible she won't want to do it again after that if it's not pleasurable for her. If she has never played with herself then she won't even know what feels good for her, but chances are she has, and is just shy and doesn't want to admit it. So give her the opportunity to tell you what she likes and if something doesn't feel good. Don't ask her every 5 seconds or anything, but let her know she can give you feedback and if she doesn't say anything for awhile then you can ask her every once in a while.
"how can i make it as painless as possible"
This is probably one of the most important times you'll need to pay close attention to foreplay. This is a very important step for women, which unfortunately many men skim through or fully pass by. By playing with her before hand she will loosen up and "get wet" which will ease most discomfort of penetration. It might not be a bad idea to have some lube on hand though, just in case.
Also, when it is time for intercourse, don't just go and try to conquer her, be gentle and slow... teasing, if you will, so as to again help her relax more. Also, probably a good idea to let her choose the position. And be responsive to her... if you're going missionary and she doesn't seem happy, try doggie, or let her be on top.. be creative, but don't try all the fancy stuff off the bat. The number one thing here is get her off!. Sure you want to too, but make sure she gets hers. Whatever it takes, fingers, mouth, toys, penis.. whatever she likes bets. This should ensure she will want to make love with you again and again. Oh, and by the way.. don't loose that rule.. always make sure she gets hers:p
Oh, and.. umm.. don't be too disappointed if she doesn't actually want to do it on your wedding night, as she may be very tired and most happy to just sleep in your arms :)