Creating classes in QuickBooks Pro

Hello everyone,

I recently started a new online business. I was told by my QuickBooks Pro Advisor that I should get familiar with the class feature in QuickBooks. So I did a little research and this is what I have accomplished so far:

I have enabled class tracking (I did this by going to edit > preferences > accounting > company preferences > and checked the box that says "use class tracking")

So now I would like to add a new class for the online business. I will keep it simple by calling it "Online Business". To add a new class you go to lists > class list > class > new. Is that the correct way to add a new class?

How will adding this new class affect the previous transactions that I have already entered in QuickBooks? I have been entering receipts and depositing funds since January 1st for the main business activity. Will I have to add a class also for the main business activity. Both businesses are part of the same corporation (they are not separate). I will create a separate corporation for the online business once it starts to make more money. I would like to separate the two business activities in QuickBooks because one deals with creating and selling art and other deals with creating and selling websites.

I am using QuickBooks Pro 2009

Thanks
Gordon