It is possible to make a tool to take the pinion out, that's what I did. I took a large fitting, with the hex head the same size as the recessed nut that holds the pinion shaft in, and cut it off and welded it to an old deep well impact socket that I had. Works great, but it can still be hard to break it loose, because it's usually pretty tight and it is hard to hold to keep the gears inside from turning unless the axle is still through the gears. Best to use an impact to get it off if you can. I can't remember for sure if it has left-hand or right-hand threads, so take this into account when trying to get it off. Maybe someone else on here can remember.
It might be a lot easier just to take it to the shop and have it done, but if you do make sure they do it right. I had one that wallowed the place where the needle bearing went in. This made the hole where the needle bearing is supposed to go too big for the new needle bearing. When this happens it is supposed to be sleeved if it's not too bad to fix. At that time, I hadn't yet made the tool to get the pinion out, so I took it to my local Honda Shop. When I got it back, they had replaced the bearings, but didn't sleeve the needle bearing. You could take your hand and wiggle the pinion back and forth almost as much as you could before they replaced the bearings. Good thing I checked, because they didn't even mention it to me. It was just as bad when I got it back as it was when I took it in. That just don't work. It's got to be done right. That's when I made my own tool and done it myself. I should have done it myself, anyway. If you do something yourself and know that you did it right, then you don't have to worry about it. When someone else is working on your stuff, a lot of times they just don't care, as long as they get the money.
