Shouldn't be too hard, BUY THE GASKET FIRST, mind, and but two of them cause they are easy to damage.....you might want to grab some permatex gasket sealer too, if the casing is a little bent.
The hard part is getting that damn pedal arm off, especially if it's a little bent, expect that to take up to an hour and a half of hammering and shouting varied obscenities, but it will, eventually come off, try not to damage the threads too badly, a rubber mallet and a wooden dowel are best tools for getting that %#$@& pin out.
Now, drain or plug the fuel lines, and drain the trans, and lay it on it's side.
Remove the outer bolts and lift the transmission cover off.
Remember which bolts went where too, because some of them are longer/shorter than others, mark with chalk or draw yourself a diagram.
Then get some ultra-fine sandpaper and gently brush-sand the contact points where the right side cover will seal against, to remove dirt, grime, old gasket pieces, etc...gently, mind.
Now, get an empty pop bottle, a rag, and a towel.
Pour some dishashing liquid in the bottle and fill it the rest of the way with water, and go back outside, pour this mixture on the rag and clean off the contact points thoroughly...you want that metal gleaming and clean, do the same to the new piece to clean off any preservation oils possibly used on it in storage.
Towel them fully dry.
This is a little more work, but it saves you the hassle of putting it all together only to find that because of one little speck of oil in the wrong place, the damn thing leaks, you know ? - you want a perfect seal.
Now, put a tiny bit of permatex on your finger and line the contact points on the trans with a very thin layer of the stuff. (careful here, some products might burn you're skin some with prolonged contact)
Now, slowly and with great patience, put the Gasket on, take your time, cause the Gasket is very fragile, and if it rips even a tiny bit, the trans will leak when you are done.
Once the Gasket is on, and you've gently pressed it to the layer of sealant, apply another thin layer to the side of the Gasket facing out now, and then place the cover in position, and slowly and gently press it down to ensure good and full contact.
Now replace the bolts, consulting your diagram or chalk marks so they go in the right holes, and tighten them down firmly.
Bring the 'ped back up on it's kickstand, and replace the pedal arm, it should be relatively easy unless the pin is very bent, or you've torn up the threads getting it out.
Unplug the fuel lines, and fill the trans appropriately, and wait 2 hours for the sealant to be wholly dry.
Then start it, let it run for about 10min in place, throttling up and down, while checking that Gasket seal...if you have no leaks, your are good to go.
Hope this helps, and happy motoring.