Set Up MarketPress Buy Now as Contact Now/Buy Now on Main Site/Contact Now on Multisite

MarketPress needs to be modified so instead of purchase functionality that Buy Now Link becomes a Contact Us Link with Contact Us pop up on Multisite Shop Areas - Multisite |Shop Sites|. Essentially the multisite shops ---Buy Now becomes contact now or inquire now --
In turn on the main site, will still offer the ability to purchase using marketpress plugin --- Needs to be modded to work as it currently works.

I require the conditional code -- PHP Syntax --- To Check for Multisite and display Contact Now - PHP inline HTML to display a different set of HTML/PHP code for Multisite Shops and display normal MarketPress Syntax - HTML/PHP Code on Main Site. Please confirm if you understand the natural order of my inquiry.

Thanks