If my facial moisturizer does not contain a sunscreen, will it reduce the SPF if I mix the moisturizer with a sunscreen prior to application or will I get the same amount of 'protection?'

I don't recommend mixing your facial moisturizer with a sunscreen. It may dilute your moisturizer and cause it not to work effectively. Apply your sunscreen first, allowing to it absorb into your skin and then apply your moisturizer. Or, you can opt for a moisturizer that contains a sunscreen.