truck makes loud humming like noise when driving, was told a bearing. which one?

What is your question?

We were told possibly the throwout bearing is bad. As you go through the gears humming just gwts louder, practically have to yell to hear each other talk over the noise. Manual doesnt name a throwout bearing. Also wont go into 3rd or 4th gear. Do we need a new transmission or pressure plate, clutch etc.