Hello, I'm hoping to find out whether we can fix this inexpensively as we are getting ready to sell the house. The unit is original to the house from 1993. It has worked fine until about a year ago. It ignites, the flame fills in all the burner ports. It stays lit for about 5 seconds and shuts down. I'm attaching a picture so you can see the components. I've read threads where some say the problem is a $500 part. Oh how I would love to hear that it's a $50 part. Any suggestions, ideas? Thanks!