I was broiled pretty good a few years ago over in alt.hvac.... and in
that time, managed to find two HVAC techs in that forum I respected.
One was Bubba, the other was Paul.

Tripntx - as an owner of a Lennox furnace, I'm BEGGING you to take
Bubba's advice. Mine is a G27M, and has gone out EVERY fall since I
bought it 4 or 5 years ago.

EVERY part has been replaced... and I MEAN EVERY PART, each visit done
by a Lennox tech. I'm not making this up....... the ONLY original part
left on the furnace is the frame, and I expect it will probably fail
too.

Out of the 12 or so techs that have visited my house - I'd say 2 were
competent. The rest were parts changers.

My point is that Lennox makes CRAP, and the companies that service them
can't even really keep up with the crap level.

Call a service tech, and WATCH THEM. Don't be a dick, but be aware of
what they are doing. You'll know pretty quickly if you got a good tech
or not.

Even if you get a "parts changer".... so what - just keep track of what
they do, and you'll know what you should be charged for.

By swapping parts yourself, you are simply setting yourself up to make
the situation much worse. I can virtually GUARANTEE that you will swap
the wrong part, and as Lennox makes such CRAP it's likely you will
break something else in the process. This isn't a slam against you -
it's just that not even Lennox repair parts are fully swappable..... on
the third installation of a new control board, they finally put in some
sort of "upgraded" model. This WAS NOT a swap out situation - wires
were cut from connectors and routed to other boards, new connectors
were installed on other wires... etc.

Take Bubbas' advice man - DO NOT attempt to repair something that can
kill you and your family in your sleep.