Sorry to be a wet blanket bud, but I sure hope you are not the main photographer if you are unsure of your gear and technique.
You may even lose your friendship if you screw up.
Ok. If you are willing to use your friendship as the gambling stake
here is the crash course :
1. Get a flash (period).
The kit lens will not cut it indoors where lighting is dim. You are asking for shaky or motion blurred shots w/o a flash.
2. If the ceiling of the wedding venue is not too high (ie. not those hotel ballrooms 2-3story high ceilings) use bounce flash (ie. flash head pointed vertically up the ceiling or near vertical).
3. For #2, get some practice at home to make sure it works.
4. Instantly review your initial shots using #2 on the day itself. If its not going to plan, go to #5
5. If the ceiling is too high, or somehow your bounce flash is still too dim, just point the flash direct and shoot. This will not be the best results, but many wedding dinner photographers do it as well, so its the safest way.
6. Always try to pop at least 2 shots per table when the bride & groom make their rounds.
Good Luck!