Clutch Replacement?

I'm new to the 2 strokes these days, I use to ride when I was younger, but now time has past and it's my sons time to rip it. I got a 2012 RM 85 that has a loud squealing noise when I release the clutch. When I pull the clutch in it stops? I just changed the gear oil and I thought maybe the oil isn't good for that clutch (Ecstar 10w-40). My thinking is it's either not the right gear oil, or I have to replace the clutch. Any thoughts out there as to what it is and what I need to do? If I need to replace the clutch, what's the best name brand clutch should I get? (My boy isn't racing big time, just a local flat track) so I'm not looking to spend $$$ on top notch parts. And also is replacing the clutch easy? Is there any special tools that I need?

Thanks,

RB