Does anyone know how to fix a Burnham Series 2 Gas Boiler Furnace??

I turned the heat off last week due to the warm weather and once it got cold again I went to turn the heat back on and of course, no such luck.  My furnace has decided to go on strike.  My husband has been trying to fix it himself for the last couple of days and of course, does not want to call anyone in because he feels that he can fix it himself!  Ha, ya right!!  So…please , if you have any tips, let me know…cuz it’s damn cold in here!