question about add-on

How easy will it be put into my system. In other words, can I put it in and use it in already saved games, or do I need to start a new park. Also, check with my local Electronic Boquie. Called and they said the 3rd. Okay, I went down today, not there so I asked them. He immediatly said the 17th. What?? I told him I called a few days ago, and it was suppose to be here yesterday. Checked computer. "Oh, it will be here tommorrow". Gonna call to make sure.

Coaster Ken