Can't recommend a shop, as I don't live in the States. There are several dealers on this forum, I am sure one of them will contact you soon by PM.

Go the turbo head on the 7 definitely.
Pro's - little more performance throughout the range for sure, and smoother idle.
Con's - Turbo plugs are a little more expensive. But if your already this far into nitro RC a few more dollars is probably the least of your worries
Go with the OS P3 plug. There are others that work good too, but this plug is a proven performer with the Go Turbo's.