L3300 Kubota crank seal replacement tips.

[backyard mechanic]

So new to me tractor w/loader and could use a little help .
Tore it down far enough to confirm main seal leaking.
Of course wasn't hard to see anyway with the oil flinging
around off the pulley and fan belt. Call it a light mist.

Couple questions having never done this particular repair before.
Its a big nut, 46mm. Will I be able to crack it with a 3/4" drive ratchet and deep socket or might it be easier to pull the radiator to get a impact wrench on it ? I would like to try the ratchet first so how would I lock the engine from turning ?
Also, diagram shows 3 pieces right there, an o-ring in furthest,
a collar, then the oil seal.
Wondering if it necessary to replace all three which i have the parts
on hand and would change all if that collar is easy enough to pull out. Just never been there done that.
Appreciate any tips and Thanks.

 

[showcrop]

I have no experience with Kubota but I would think that having the radiator in the way would add a major degree of difficulty to the job.