A good LBS will cut the steerer to the customer's requirements. Many will cut them as long as possible to safely have a maximum number of spacers (carbon steerers have a recommended maximum) and then shorten them later as requested.

I agree that putting the spacers above the stem is the best short term method. That way if you change your mind you can put some or all of them back below the stem.

Cutting a steerer is a pretty straightforward procedure. A sharp fine tooth (32tpi or more) hacksaw blade and cutting quide (a stainless steel worm clamp is a good one) are all you need. Steel and Al steerers are easy but carbon requires a bit more care.

Remember, once it's cut there is no going back so be SURE you have the length you want.