Rough Tranny

I have another question for everyone. WHat could possibly make the gears shift hard. Its a 2000 F-250 with a 5 speed manual. The gears dont go in very smoothly and the truck has 140,000 miles on it. Especially thirde gear its hard to get it in gear without a slight grind. I dont think the clutch has ever been replaced. Could this be the reason why the gears dont shift very smoothly?

Yes, if the pilot bearing gets sticky the input shaft will continue to turn at engine speed making shifting difficult.

More importantly, with 140K on it, when was the trans oil changed and is it full of the proper lubricant?