In short, install the XAP file via sllauncher.exe.
Q: What files are needed?
%%A: nothing but the XAP file. The MSVS project build creates the XAP in the Bin/Debug folder. You can give it to users.
Q: Can I send the file(s) to a user by email attachment?
%%A: I think so. User need to have Silverlight installed.
Q: User needs to go online?