My son’s Sportsman 300????

I just picked up a Sportsman 300 for my son and have a few questions. What kind / size tires should I get for him. We trail ride mostly with occasional mud. Well he loves mud. Also do they make A-arm guards for the 300. Do they have a bumper for the front of the quad. This is our first Polaris and I am not familiar with this brand. Thank you!