1) The gears are available very inexpensively on a popular auction site

. I would suggest ordering both options, then you will have the one you need on hand and will be out all of $6.
2) The second post above (Wiseman) details how to remove the gauge cluster without taking off the steering wheel. It is a challenge the first time you do it - but in my opinion not really difficult unless you have unusually large hands/fingers.
The gauge cluster slides out pretty easily without the wheel removed. It has to be angled - so left side of the cluster (temp) pushed in and right side (volts) pulled out so that it's at like a 30-45 degree angle relative to how it sits when installed. Then a little pressure on the lower dash and it comes right out. It's actually pretty obvious once you get to that step how it comes out. Just needs a little wiggling sometimes. The right side white connector is vulnerable but I've found that as long as you don't force it and just finesse it, it's not at risk of breaking.
I timed myself last time and I got the cluster out in 6 minutes, inclusive of removing the vent surround, without pulling the wheel. Did my whole odo gear replacement in 40 min flat.
While you're in there - it's a great time to R&R the gauge lights and also clean the gauge grounds. The four "footballs" come off and you can clean the copper grounds with some isopropyl alcohol or contact cleaner. My fuel gauge actually goes to 4/4 now.
Also - I would very strongly recommend magnetizing your screwdriver before removing the cluster. It is a major pain to drop a screw into the abyss of the lower dash. And - the two L sided screws do not have to be removed - just loosened as the cluster is slotted.