Theres much specualtion about the causes of premature wear to Honda CR450F titanium intake valves. But it is common and can eventually lead to hard starting.
Kibblewhite is making White Diamond brand valves for the CRF. They are made of stainless steel and are more durable. Because the stainless material is heavier than titanium, stiffer springs must also be installed. Right now Kibblewhite is working hard to fill demand.
Changing the valves require the following materials;
TOOLS - Basic sockets to disassemble the head, an inch/pounds torque wrench, narrow feeler gauge set, and a KOWA valve spring compressor.
PARTS - Head gasket, valve stem seals, cam chain tensioner gasket, either OEM Honda valves or aftermarket Kibblewhite valves and springs. Some valve shims may also be needed to accomodate the new valves.
I can't provide you with sales information because this is a forum but my site has basic prices. The fact is your local Honda dealer has the tools and techs to swap the valves and seals, and re-shim the valve to cam clearance.
Good luck