Yes there is a gasket on the side cover and you will have to replace it it's almost impossible to get the side off without tearing it.Should only be about 7$. I'm not sure on the oring or seal. A owners manual is definetly worth the money. I'm still waiting for mine to come in the mail(They cant print them fast enough wont be until next month somtime). we have a service manual for my wifes warrior. They are definetly worth there weight in gold even just for regular maintenance.
400EX- Renthal Bars,MotionPro Twist Throttle,Pro Design Kill Switch,AC Mudscreen Frt Bmpr,AC Fullbody Skid,AC Swingarm Skid,AC Pro-Peg Nerf Bars,Steel braided brake lines,Denton steering stabilizer,Raptor EZ-Pull Cluth Lever,Maier Universal XC Handguards,White bros. E-series Pro-Meg Exhaust,K&N Air Filter w/outerwear,Works Shocks w/Shockwears,Wiseco 440 kit, Hotcam,Eichner series Edlbrock carb,Hinson clutch and basket,6 degree timing key,FST oilcooler,Oversized oil tank