I need some help from any one who has or has worked on a honda 440ex. I have alot of questions, and any help will be greatly appreciated!

I have a '99 Honda 400ex, it is basicly stock, with the exception of a few bolt on skid plats and a kevlar clutch. After years of just down right abuse, (and I mean ABUSE!) the motor has started burning oil and when I am beating on it, some times I notice that when I am letting my clutch out really fast when the motor is revved high it squeels, the clutch is working fine with no slipping when I am riding. Could this be my clutch making noise? what do I do to fix it? I would like to upgrade to a wiseco 440 11:1. I have been told by my dealer that I would also have to open the air box, bolt on a larger carb to feed my machine and also purchase an exhaust that is ment for the 440. They say that a cam will also be needed. If I was to just run my machine on 92 octane pump gas, with the air box lid off, what size carberator should I use? Is bigger better? What type of cam should I use? And what exhaust will work. I ride where noise restrictions are in place and have to have a stamped us forestry approved spark arrester on my exhaust. I also would like to know, I have really punished this machine in its stock form and have really been impressed with how reliable it has been, will I loose some of that reliabilty if I modify my motor? Are there any other mods that I should use with this machine? Funding is limited, so each item will be purchased seperatly as I slowly make some money to invest in this machine, so what order should I get them in?