Lennox whisper heat furnace problems

[matchbox007]

furnace is a,
Lennox Whisper Heat
S/N 5899G26530
M/N G20Q3/4E-100-7
60 HERTZ
PHASE 1
G776RGD/intermittent pilot igniton control

I don't know much about furnaces so I hope someone can help me. The problem I am having is that once the furnace reaches it set temp on the thermastate it shuts of like it should, but once the temp drops and it should start again it sometimes starts without flaming up just blowing cold air. So I switch the unit off then turn it back on and it will retry starting wich it sometime dose and sometimes I have to switch it off and on again to get it to retry. I am getting a flashing led which says that it is retrying, but it never dose and it just powers off, which says ground fault or other problem. So my question is what course of action can I take before I shell out money for a repair man. Oh and I live in Alberta Canada an it is -40c so if someone can help me soon that would be great I can't get a repair guy for 7 more days. Thanks.