Its been a while since I worked on brush hog to replace seals. Last one belonged to somebody else, 7ft monster, heavy as all get out.
I will say if you have any common sense and a way to do it, lay the thing over on its back rather than trying to work from underneath. Wont hurt the mower to do this. Common sense is necessary doing anything like this. If no common sense, hire a shop to do it.
There is a heavy bar that goes on tapered gearbox shaft, the blades attach to each end of bar. The stump jumper pan is usually welded to this bar especially on smaller mowers, though some have stump jumper bolted on to the bar. If bolted, you would just unbolt it from the bar. But if its welded to the bar (most likely), you will have to remove bar from the gearbox shaft. Maybe splined shaft or tapered shaft with key.
The way this is usually done is with special puller or you can use long heavy bar of iron with couple hole that match up with the holes where the blades attach.
Way I did last one was to buy couple large diameter bolts along with couple nuts that fit them. Nothing special just largest diameter bolts TSC sold in their bulk bolts. I welded the nuts to the bar, one on each side of the center hole that fits on gear box shaft. Used bolts and couple pieces say 6 inch lengths steel bar that spanned the bolts to make a homemade puller. Worked great and I didnt need some long monster bar of steel that went from one blade attachment hole to the other. The longer the span, the heavier the bars steel needed.
What I am saying is you either need a special puller or you need to have capability to fabricate an alternative puller. Unless somebody has been removing the blade assembly on regular basis and lubing the hub/shaft, then just banging on things with a hammer isnt going to work.
And if you are really wise, while you have whole assembly removed from the gearbox shaft, you will replace the seal whether it needs it or not. Save labor of having to take all this apart a second time.
Here are examples of two welded ones.
Here is an example of a bolt on one or at least this pic I found looks like its a bolt on.
Nope, my eyesight is getting bad I guess, those are welds along bar I am seeing that show through.