no start!!!!

[bluefever]

have an '01 camry with the 5s-fe 4 cylinder,did plugs,wires,filters few months ago.about a month ago it started having trouble running if you didn't let it warm up for atleast 10 minutes before trying to drive it,it would stall.Seemed like most of the times it through fits the most was the morning after it rained.Now today,it won't start,I can smell gas.The cel is on some codes repeat themselves, but this is what comes up - P0300 Random Misfire detected
P0420 Catalyst System Efficiency Below Threshold(Bank 1)
P0446 Evaporative Emission System Vent Control Circuit
P0300 Random Misfire Detected
P0446 Evaporative Emission System Vent Cpntrol Circuit -also it sounds as if it backfires.someone will probably suggest sending it to a shop,but is there anything that could be checked beforehand???

[BMR]

Check to see if it has spark - remove a plug, insert it into the plug boot, lay the bottom of the plug on a grounded surface, crank the engine, & look for spark in the gap.