Late 20's, Im mid 30's, less than 10 years separate us. I still paly 40's big band, swing, jazz, 50's Rock and Roll, Doo Wop, Motown etc. Point is, you obviously have decided to become a DJ. You cannot use the " way before my time" excuse. The client could care less if you are taking their money. So its a good sign that you are seeking help.
I may sound redundant as I have said this many times. Even i f you hate a prticular Genre of Music, go find the radio station that plays nothing but that and listen to it for 1 week. the next week, listen to another station that you are unfamiliar with, and so on...
This is your "Homework" as a DJ. It keeps you sharp and updated.
Then you do searches on gig logs on forums like this and read the set lists. When you see particular sets of song, you knw automatically that it belongs to a particular genre. Take note of that and try mixing them at home. Then you get a feel of how these will work in given situations.
We really dont mind sharing set lists, this is just some advice to hone your skills and music knowledge. Being a DJ is fun, its also a lot of responsibilty.
It works the opposit way too. A lot more " Mature" ( ahemm... older) guys are forced into listening to todays Hip Hop that does nothing but make refernce to their Bitches and ho's and their shawty's. Do you think they enjoy it? Probably not, but they have to stay updated. So there!
I still ask stupid questions here and there, but the only stupid question is the one you dont ask so dont feel intimidated.
Good luck on the gig, take a dump before you leave the house, dont get wasted and have fun.