Inherited Dryer Runs but just stopped drying

We inherited a Kenmore gas dryer with the house we bought back in March 2007 so I don’t know how old it is. Until yesterday it was working fine–now it runs but will not heat up at all. I have seen seen a number of possibilities on this site (thermal fuse, heating element, etc.) but I am a novice and don’t know where to begin. We’re thinking of replacing it since Sears charges $60 just to look at it and we both assume any additional repair cost might be better put toward a new dryer. Any ideas? If it helps the serial # is ML3401979 and type is DDOT-NAT-1206006-CV22. I’d like to know how old it is and would greatly appreciate specific details on any suggestions on how to troubleshoot. Thanks.