My daughter's one roommate is Full Service Food and Beverage Hostess. She works in the Crystal Palace, greeting guests and seating them. Basically, that is the Hostess role. You will be assigned a table service restaurant in one of the parks, possibly in one of the resort hotels. My daughter's roommate loves her role!
As far as the building, you don't get a choice; they assign you the building based on your arrival date and your number of bedrooms preference. My daughter had hoped to get Chatham, primarily because of the data jack. But everyone on her arrival date went to Vista. I'm sure there are good and bad points for each complex. The extra data jack and more cable stations in Chatham. The buses run to the final destinations from Vista. People in Chatham need to catch a bus from Chatham to Vista and then catch another bus to their final destination. So Vista has the edge there. Wendy's, Chick-Fil-A, and Walgreen's are a half block away from Vista. Chatham, put on your hiking boots. Laundry facilities are in every building at Vista; Chatham has central laundry facilities. Hot tubs are only at Vista.
After the intial disappointment in Vista, my daughter and her roommates decided they really like their apartment in Vista and are glad they got it, despite the lack of a data jack and fewer cable tv stations.
Clothing guidelines are on the WDWCP website once she has a login. Casual is fine, but you do need business casual for Traditions and the training sessions. Dressy is needed for graduation.
I waited with other parents while my daughter checked-in at the various stations. Then we went to her apartment and started moving everything in. I do recommend you get a car for the time you are there. It will help get all her stuff to the apartment and also help when you want to meet up with her. Plus it will be of great help to do an initial grocery trip and maybe Target or
Walmart for anything else she might need. That first day there, I ended up taking 3 out of the 4 girls in the apartment to Target and the grocery store. The following day, I took them all to Property Control where they found some posters and little things to help decorate the apartment Disney style! My car got them to Property Control; their WDWCP ids got me in there!

We also were able to go shoe shopping once she got her actual assignment.
Parents can be seen throughout the complex that first day. And some even attended the first night welcome picnic.
Safetymom, my daughter loves to call me and tell me what she just got to do, too! She has over 30 visits to WDW under her belt so she doesn't need any more Disney secrets from me.

One of my favorite calls from her was from the MK CM parking lot as the fireworks were going off. Everytime they had another big boom, more car alarms went off!

She was so excited, and still is, when she calls to tell me about her day at Disney as a WDWCP'er.