I would guess the first shop is not the place to take it. I am going to suggest you have the carb cleaned. You could try using SeaFoam... but I am going to guess a proper carb-off-the-bike, remove-both-jets cleaning would get you better performance.
When the bike sat for several month or longer, the gas/ethanol mixture we get in the US now separates and a rather stubborn varnish collects in the carb of smaller engines. This is why the dealer suggested "just ride it". If you ride it, the gas will eventually clean out the varnish. But if it not ridden enough or the jets are plugged too much, they never get clean enough for the bike to run well. This suggestion also works better for larger jets in larger carbs.. like in Harleys. Your scooter is using one half or less the gas with an engine 1/4 or 1/8 the engine size (in cc)