Hi Ricky,
Everyone has their own method that works best for them, here's what I did when I recently did the job you are doing.
Wire wheel or emery cloth the the axle, remove all the oil grease and rust, when smooth, apply a bunch of multi purpose grease on the axle, it will make sliding the wheel off the axle a breeze. The wheel assy will be heavy, if the tire is loaded with water inside it will be EXTREMELY heavy, be careful.
Remove the bolts on the wheel center clamp and remove the wheel.
Remove the bolts on the bearing retainer, you might have to tap on it with a hammer to loosen it, slide it off the axle, the bearing will remain on the tractor inside the housing, so you wont have to worry about damaging it.
With the retainer off the tractor, set it in a large vise if you have one, and knock the old seal out through the backside, if you don't have a vice, a block of wood under each side of the retainer will give you enough room to drive the seal out.
There is a felt seal as well under the oil seal in the retainer, remove it as well.
Clean the bearing retainer, bolts, and the bearing cavity area with your favorite solvent, wire wheel the mating surfaces of the bearing retainer and axle housing, make sure the old gasket is off, then, wire wheel or emery cloth the area on the axle shaft where the clamp was, you want the entire axle to be smooth of any burrs or gouges prior to installing the new seal.
New parts, you need the oil seal, the felt retainer, and the gasket for the retainer. I would put a new grease zerk on the bearing retainer, and make sure to clean the old dried grease out of the passage.
Rub a good amount of grease on the new felt seal and lay it in the retainer.
I put a very small amount of silicone on the the outside of the oil seal, install the oil seal in the proper direction, on top of the felt, until the seal is seated in it's cavity. Make sure you drive the seal in straight, do not let it get cocked at an angle. If you are not sure about installing the seal correctly, google or search you tube for pictures and video till you are comfortable, it's not hard, just needs to be done right.
Take a clean rag and wipe any dirt or chunks off of the axle shaft, then put a clean layer of grease on the axle from the bearing, outward to the end of the shaft, doesn't have to be much, you just don't want to gall the seal lip when installing the seal.
Pack the bearing and cavity with grease.
Put a small amount of silicone or #2 permatex on both sides of the retainer gasket, put the gasket on the retainer and use a couple of the mounting bolts to hold in place.
Slowly install the seal/retainer assy on the axle, rotating it slightly as you push it on, the grease and your prep of the axle should ensure that you don't damage the seal.
With the new grease zerk pointing straight up, press the retainer against the axle housing and install/ tighten the 4 bolts.
Wire brush any rust and dirt out of the inside of the axle clamp on the wheel center, a little more grease on the axle will make it easier to slide the assy back on.
Once you get the wheel to the right spot on the axle , tighten the snot out of the clamp bolts.
With the wheel still off the ground, put a couple pumps of grease in the new zerk fitting you installed on the bearing retainer, rotate the wheel a few turns and put a couple more pumps of grease in.
You should be good to go.
I recently replaced all the differential seals and brake bands on my '40 H, it was a lot of work, mostly cleaning all the old grease and crud from all the years of leaking. My tractor is rusty and faded but runs like a top, makes me feel all warm inside when I see how it looks now though, compared to the condition it was in when I brought her home years ago.
Good luck to you, and have fun...Tom