Goodman GMP075-3 installed in 1993. The igniter did not light up. I measured its resistance and it was 75 ohms. Then I touched it lightly with a screwdriver and it felled apart. Is it normally so brittle or just when it is old and bad? I was looking on-line to purchase new igniter and found so many brands from $23 up. White-Rodgers 767A-845 for $24, Rheem 62-22441-01 for $23 etc. Are these brands good or should I buy brand name and spent more? Also, I would like to know if the igniter does not fix the problem what would be next troubleshooting steps and how to read and interpret the blinking light codes. 2 times in the last few weeks the heater blower turned on for no apparent reason. The furnace is in my past residence which is now rented and 80 miles away so I need to be ready with all possibilities before going there. Any help will be appreciated.

Yes they are very brittle, also they shouldn`t be touched when installing ,handle by the base only
Chances are it was bad and had a crack in it before you broke it,be extra careful with the new one as you are installing
When you purchase one just tell the make and model number of the furnace