used sunfire code/dealer problem need help

I purchased a 2003 pontiac sunfire with 101300k not 10min after picking up the check engine light came on. Dealer checked it was a code440(evap emission)he changed the gas cap and re set light. Light came on 2 days later. I have been back and forth for him to have this checked and he,s playing games, more interested in inviting me fro drinks or lunch which I have all on emails.I am just outside of the Toronto Ont. area. I can have the UCDA do a mediation but I have to find out why I have the code and get an estimate which is getting pretty expensive and ticks me off the I can,t make this guy do it.I have found a small independant mech. very good but can,t do every test. He has scanned and gotten the 440 code and then checked with the Tech2. He knows the purge solenoid is working but has no response from the vent solenoid. Could getting this fixed fix the problem or could there also be a second thing going.My mech. is not set up for a smoke test.If I knew for sure it was the vent solenoid I would just get that estimate and try the mediate.He also was to do a emissions test and did not do one, he said it had just been done in the last year maybe he thought with the check engine light on it would not pass so didn,t do it.I feel like this guy holds all the cards. San