What happens if you put city water to the system? Do all the faucets flow well? maybe try unscrewing the aerators out of the tips of the faucets and then run the city water through for a fer minuted to flush out any possible debris. Then try the pump again.
My guess is the valves are in the wrong positions. I'm basing this solely on the fact that it is winterized meaning that the pump did work at one point.
Before I pulled it back to the dealer I would probably figure out how much it would cost me in fuel to do so. Keep in mind that the dealer might not be able to fix it the same day necessitating a second round trip. If it's a 240 mile round trip (4 hrs @ 60mph) then take 240/10 (figure 10 MPG towing) * the price for a gallon of fuel (figure 3 dollars a gallon) and you get 240/10 = 24 * 3 = $72.00 plus a whole day wasted pulling back and forth.
At that cost I would buy a $60 PEX crimper and some PEX hose clamps from Home Depot and take the connections apart at the valves and pump. It's possible that one of the valves is installed backwards and therefore the labeling is incorrect. Take the system apart and you should be able to figure it out fairly quickly. Then using your new crimper put it all back together where it makes sense.
Actually I have a better idea. Call the dealer and explain the issue. Ask the service guy to snap a picture of a system with the valves in the correct position for normal use and text you the picture.
