Will verifying Shoptoit for Google access revoke my own in webmaster tools?

We will not be the sole owner for your domain in Google, you are simply allowing us permission in addition to your existing verified owners. This is the only way Google allows us to feed your products to PLAs. 

However, if you are already submitting a feed to Google for Product Listing Ads, you will not be able to send an additional one through shoptoit. Google allows only one product feed per domain.