What passport are you holding? You say you are leaving from ICN--are you (South) Korean? Or "First World" country passport holder? If so, I wouldn't worry about getting a visa just for this transit. Seriously. If you need to go through immigration, you'll need to show your passport and boarding pass for PVG-SIN segment--just say "transit"--the officer will check your documents and process you accordingly. In the event you cannot be issued a boarding pass in ICN for the PVG-SIN segment, make sure you keep a copy of your confirmed itinerary handy with your passport. Perhaps some of the PVG experts can chime in here, whether there is a "transfer desk" on the arrivals side BEFORE you get to immigration, where you can get the boarding pass. What airline(s) are you booked on, both coming in and going out of PVG?

Now, if you hold a passport from certain countries, you may have more of an issue. But for most, transiting is mostly just jumping through some Chinese hoops and some physical exertion, but hardly scary.