Thats the cylinder base gasket, and its hard to tell from that picture what that is. Clean up the bike really well and trace where the leak is coming from. Also, if a gasket is failing, the compression should reflect that. Have you checked the compression?
All in all if you need to replace it I wouldn't sweat it too much. The Blast is quite simple and straightforward in design and very accessible. The only pain would be having to replace all the gaskets in between all the layers.
I agree with Stang - if its not bad, and compression good, don't sweat it. Blasts are tanks, with the exception of the boot and the front motor mount.