Resurrecting a quad that's been sitting for a few years
 

I finally convinced my brother to give me his 2000 TRX 400EX that has been sitting in his garage with a blown head gasket for at least 3 years. He's sure it's got a blown head gasket and a 440 kit in it. I am thinking I will probably replace the whole top end with a new 440 kit (cylinder, 11:1 piston, gaskets, ect) so I don't have to worry about cracks in bad cylinder walls / sleeve installation. Hopefully it also has some other work done so that I don't have to get everything it needs to scream ie. jetting, air filter and pipe.
My Question is what else should I look out for, test, clean or replace (beside the air filter) for a bike that has been sitting this long? I'm mostly concerend with motor stuff, shocks and breaks can come later. It's been pretty well protected because it's been in a garage this whole time.

Thanks for your help, lovin' the forum!

From what I have heard about the 440 kit, it's not good. The engine has a short lifespan. If it were me, I' replace to jug, piston, rings etc. with stock, then jet and pipe for performance from there. I don't like the 440.

I read the same thing here but I'm not going to sleeve the existing or a stock jug. I'm planning on getting the cylinder that's designed for 440 aftermarket.