From my other post. I would check this first before you buy something.
I would check for a dirty or cracked spark probe assembly? In the manual it will tell you how to check the integrity of the spark probe. If you can hear the spark then I wouldn’t suspect a bad board. Basically when it is dry out, you turn the gas off and insert an insulating material between the sparking and ground probe gap and this might force the spark to jump where it would if it is damp out? If you do it when it is dark out, it would be easier to see the spark.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27001654.cfm