Do spacers alter safety or performance of wheel?

[Fore]

I just ordered TireRack snows to put on my 17 factory wheels on a 2007 335 cab and I am looking at ZHP wheels for sale (Style M135s) to put on for my summer wheels. If I add spacers, will it alter the safety/integrity/performance? Also, what are the costs and do I just get them from a tire shop?

Thanks for any help.

Jon
07 335ci Space Gray/Saddle