newbie w/ question

First off- hello everyone! (and sorry for how long this turned out after I typed it all up)

Long story short, I got super sick of having long hair ( talking right above my butt). First cut I had it done in a choppy layered cut that landed right above my shoulders, had it for like three days figured, hey I like short hair l'll go get it cut to the bottom of my ears, ( I wanted something short enough i could spike out the ends yet still have hair). The woman I usally have do my hair wasnt there and in a moment of stupidity I had this other girl do it, needless to say I walked out of there with what she called an A line cut ( long in the front super short in the back) so I left with an extremly punkish cut.. that I hated then and hate now...

Its been about six months so its pretty much grown out of that only thing to do is spike it look stage, however I was informed that my hair is long enough for extensions now. One place I went said they would only do a sew in on my hair another place said she could do a sew in or glue them in.. I did read all the topics in this fourm, and Im still super confused..

I want hair thats like a little past my shoulders, and black to match my hair since Im lazy and I only color it once a month Would it be better to have it sew in or glued in, whats going to be better to my hair?

Im in school right now and in labs we have to wear our hair up under our hats (in Culinary School, dont think anyone wants hair in thier food..haha) and when I go to the gym my hair has to be off my neck at all costs ( talk about using a ton of bobby pins right now) So I need something that doesnt show super bad when pulled up/back. And as stupid as this sounds ( and since I always seem to forget when to ask when Im at the shop) once I get extensions how often can I wash my hair? I wash it like twice a day now, and I seriously think Id have issues having unclean hair. The only person I know who has extensions is a girl I work with and shes African-American, and I know she gets hers washed only when she has her braids taken out and redone, I dont know if that makes a difference, since I wouldnt be having braids done .. sorry for the stupid questions and the rambling, Just going to vegas for my birthday and I wanna have hair when I go dancing, something about no hair and dancing dont mix (for me) ahha ..

thanks!

~jo