Grinding Third and other issues

So just recently the car started to grind third on occasion. It seems to do it more when I shift fast. If I shift slower it wont do it. Also it seems harder to get the car into second at times on the 1-2 shift. Sometimes the car will shift fine and act like nothing is wrong, but other times it does the above mentioned things. When the car is cold I also notice a grinding sound when I put the car in first of second gear. The gears themselves are not grinding but there is some sort of humming noise that I can feel in the shifter. It's hard to explain. Also there is a rattling sound when the car is idling in neutral and it goes away when I push the clutch in. So, what could be the problem here? Is my tranny going out? Are the synchros bad? Would changing the fluid in the transmission help anything? For what it's worth the car has 67k on it.

Also, the car sometimes will shift fine and everything seems ok. Since the weather has gotten warmer it is not doing it as much for some reason. Could a throwout bearing cause it to grind at times? Thanks for the help.

I'm no expert, but I'd check the fluid level...if it is good, what color is it? May be time to change the fluid. Good Luck!

Anyone else? The fluid level is good. Not leaking anything.

There is now a humming type noise that I can hear and feel in the shifter and clutch peddle and it will do it in every gear now. Sometimes it will shift fine, other times it does this. Also sometimes when I idle in neutral it will then be hard to get into first and sometimes wont want to go in. The rattling still occurs when the car is idling in neutral and stops when I push the clutch in. The clutch seems good still, no slipping or anything. I am guessing the throwout bearing is bad. Would this cause it to grind in some of the gears and be hard to get into gear? It rarely grinds at all now but this vibration/humming thing has gotten a little worse. Like I said earlier, sometimes it drives normal like nothing is wrong. Maybe the whole clutch needs replaced? Thanks for the help.