2003 Toyota Tacoma Brakes and Clutch?

First off my brakes have quit. There is fluid but they dont work. Could this be air in the lines? Second when the truck I soff I can put it in gear but if turned on while in gear it just jumps. If its running and out of gear I cannot get it to o in gear. Its not slipping or missing the gears its just not going in. Is this the clutch or the slave cylinder? Someone has looked at it and said the cylinder was fine so they think its the clutch but my ex swears it to be the slave cylinder however he is not hear to look at it and im not familiar with this kinds of problems. The truck ran fine the next morning is when all this went wrong.