Installing Sims2 Best of Business...help!

[pinkwave]

Hi guys!  I just purchased The Sims2 Best of Business collection, but I'm terrified to install it  {ohmy} I've read the directions, but I'm still not sure what to do? I'm afraid I'm going to lose the game I'm playing now or screw it up some how. I have The Sims2 Double Deluxe installed now and I've been playing for ages. Somehow, I was under the impression I could just install this new collection and everything would neatly fall into place with my original game. Apparently, not so!  {no} Right now I have the aging off cheat on. Do I have to turn that off? and backing up files? huh? duh?  {unsure}

Would someone be kind enough to walk me through this very scary procedure?  {freaked} Please make in simple. I'm not too computer savvy.  {blush}

Thanks in advance.