2000 Dodge Intrepid • 195,100 miles

I'm getting error code p0455, indicating a leak in the EVAP control system. I just spent a ton on other repairs and would like to troubleshoot and try to fix this myself. I replaced the gas cap and had the check engine light reset. It was ok for about a week, then came back on with the same code.
I've read about a "smoke test" - have no idea what that would cost. Can you tell me how to track down a leak myself and what I might have to replace? It's not really covered in my Haynes manual.
March 14, 2013.

P0455 Evaporative Emission Control System Leak Detected (gross leak)

The gas cap is a logical suspect. A big leak can often be found with a visual inspection. Look for a rusted-off hose clamp or a disconnected or rotted hose. You can check for a smoke machine at an auto parts store that rents or borrows tools. That will allow you to inject a white non-toxic smoke at two pounds of pressure into the system, then you look for where it's sneaking out.

Mar 14, 2013.