Ok, I'll lay this out best I can.
In this picture below polaris has this layout wrong. it's wrong on my ranger and it's wrong for the 2014 midsize.
It shows you need two of number 20, when in fact you need two of number 57 and only one of #20
if you're going to use aftermarket bearings, I'll help you understand which ones replace what as best I can
a 6203 bearing replaces #24 (3234274). You'll need 2
a 6204 bearing replaces #20 (3233018 ). You need 1
a 6205 bearing replaces #57 (3233019). You need 2
a 6207 bearing replaces #22 (3233009). You need 1
While you're there you may want to replace the input shaft seal -3234851 . kinda pricy. I didn't replace it on mine because mine looked good. It is replaceable without removing the transmission if it would happen to leak later on. Usually when an input shaft bearing fails it ruins this seal. I don't see a seal for the park brake rotor shaft like I have for my 2011. Does your midsize have a park brake? or maybe it's got park in the trans?
before you take the trans apart, I'd take the selector shift fork off of the RH side along with the cover and 3 gears inside. Then split the trans, and before pulling the selector/ low reverse shafts out, I had good luck zip tying the selector shaft (the one with the shift forks) to the shaft that has the engagement dogs on it. Then they pull out together without coming apart.
To get the low/reverse chain off which you will need to do so you can replace bearings, you'll need to remove one bearing and a snap ring if I remember right. Be careful not to bind the low reverse chain too much.
getting the drive gear and lower bearing off of the main chain drive shaft was kind of a stinker. I did it with two adjustable heel bars and a vice. It's best if you have a bearing puller. One recommendation, never re-use a bearing that you've pulled off. no matter how good it looks.
You can check the bearings by spinning them. if they feel gritty or don't spin free, they're on their last leg.
Going back together I had to zip tie my tentioner back to the main gear case to take the pre-load off of my main chain so I could get the top half of the cover back on. just before the cover was all the way down, I cut the zip tie, pulled it out, and put some extra silicone there. Not sure how the guy did it in the video, never watched it that far in.
I recommend using permatex ultra grey silicone I love this stuff. I used to use the ultra copper which is good, but the grey is stiffer and seems to stay in place better. I use it on everything now.
I'd watch those videos through, and if you have questions give me a shout, I'll help as best I can.-