You have hopefully only toasted a clutch and not the gear itself.
The toughest part about tearing down the lower unit on an older motor is getting the bearing carrier out - they are often corroded into the gear housing - but with enough "persuasion" - and swearing loudly often convinces the part to co-operate" - they can usually be pulled.
On this model the carrier just slides in/out, so it can be removed with a puller which can usually overcome all but the very worst corrosion.
You will also need a special socket to aid in the removal and replacement of the pinion gear (which you need to remove to get the rest of the "guts" out). Since there is no room to operate a wrench in the gear case itself (and I have tried) there is a socket that goes over the driveshaft splines (that normally mate into the crankshaft) - you could get away with using a pipewrench or vice grips during the removal process, but absolutely need the socket for reassembly since the pinion nut must be precisely torqued down.
If you do get in there and find that anything other than the clutch needs replacing, then you open a whole new can of worms.
Any gears that are replaced require shimming and backlash checks which is best done at a shop with experience because a minor "boo-boo" and your new 300 dollar gearset is "junk" the first time you fire up the motor.
So at least on this particular model, the clutch is a "diy" project, gear replacement should be restricted to the pro's.
