I find the "my guy" at the shop highly questionable from the get-go. Chains are known to wear into the shape of the cassette/freewheel/chain-rings. This means that if you replace the cassette or chain-rings, the old chain will not work well at all. So a new chain is called for whenever you change out those parts. Replacing the cassette and/or chain-rings because you got a new chain??

I smell a capitalist rat. I'd just put on a new chain and go for a ride. If all goes well, then you can merrily upgrade at your leisure, not under duress brought on by high-pressure sales tactics by someone who is not being altogether honest with the customer. Get the chain. Take a ride. And get a second opinion - but don't tell the mechanic at a different shop that you already had another guy/girl look at it.

Good luck!