How can I see what will happen to my tax liability without loosing all the data I've saved on my Sched. C by not reporting and closing my personal business?

Since you are using TurboTax Home & Business installed on your own computer, you can save your current return with a new name. (Or copy the .tax20XX file with a new name.) Then work on the copy to make any changes you wish to test. The original file will not be affected.

If you wish to remove a Schedule C business entirely, go to the Business tab, select Business Income & Expenses, continue to the list of businesses, then click Delete beside the business you wish to remove. This action is permanent, unless you have already saved a copy of your return.