tikel, use the search button on this site. There's plenty of tutoritals around. se-nse also have a few guides there.

1) It depends on the method that was used to unlock it. However, flashing it with a firmware and FS, usually won't disable the unlock. The unlock is in the GDFS area.

2) Yes, messing with your phone is risky business. you may "brick" your phone, meaning it will be unusable. If you're not too sure about what you're doing, don't do it. Safest way is to cough-up some money and bring it to a cellphone shop or do it with wotan or davinci. However, if you read all the tutorials and do a lot of research here, you can debrand it for free (at your own risk). It's usually a success and the process of debranding isn't too hard.