I've done over half a dozen rear mods. It's easy as long as you're careful.
I call it a rear translplant, and you'll need some glue. I prefer gel super glue, but regular super glue or model glue is fine.
Most wheels pull off easily if you pull evenly and twist.
I hold the center of the axle with needle nose pliers, to that if i rough up the axle it not where it has to ride! be careful not to bend the axle, it isn't good.
In your case, you are only transplanting the drive gear itself onto your favorite rear, so you only need to remove the wheel on the gear side. You'll get practice too, because you'll have to repeat the process to remove the drive gear from the MS rear too!

If need be, make a mark with a sharpie or even a pencil where the drive gear was, so you can line the new one up.
It's easy once you've done it. Anyone who says otherwise is a big wimp.
My favorite is the 8.25:1 combo (lightish green/teal) for pure speed.
BTW For an example of my latest work, take a look at
THIS