Sorry about your brother....Lets see what we can do to help you. The only other things I can think of off hand would be new spark plug and change transmission oil. If this is a 4x4 you will want to look at the rear differential oil and front hub oils too. I am guessing that you already checked the obvious things like air filter, wheel bearings and tie rod ends. So if everything else checks out go ride!
Mine: 2018 Sportsman 850SP - 26" Bear Claw HTRs on OEM steel wheels(I really don't like the Aluminum ones)
Polaris Hand warmers, Mirrors.
Hers: 2007 Sportsman 500 EFI, Polaris Winch, 26" Bear Claw HTRs on Moose 427x Wheels. QSC Clutch Kit, Hand Warmers
2001 Magnum 325 MOSE 12" rear wheel conversion. 25" Sedona Coyote tires
2001 Magnum 325 Warn winch and Moose 60" plow
2017 Polaris Ranger 1000XP - Roof and front glass
SOLD 2004 Sportsman 600 Twin