Changing out the ignition coils is an easy DIY project. OEM Beru brand coils are available for US$46.00 each from Pelican Parts. I and many others have found them to be a reliable source.
http://www.pelicanparts.com/catalog/shopcart/986M_catalog.htm
Another good source is ************************************************************. They have the Berus for US$40.46each.
Why do you think some or all of your coils are bad?