1. No, your data is saved to your iPhone, just accessible from your Apple Watch once paired.
2. Apple Watch app, tap on the "i" beside your watch and will see the option on the next screen. Re-pairing the Watch will be the same as when you first set it up.
FYI - Once re-pairing your watch, you will be presented with an option to restore from backup or setup as new. With both you will have access to your old data, but restoring from a backup retains your current settings. Setting up as new just gives you a fresh start minus your settings. Oh yea, the process takes a while.
Hope this helps.