the knocking I'm not sure but you should check your gearbox mounts as the box can hit the floor if theyre broken of loose. its hard to diagnose without much information though.
the speedo squealing is in the speedo, I've seen two do it so far. I had spare speedos so I just changed them, but you can try spraying some lubricant of some kind into the back if you want.. dont try to disassemble it though cos it doesnt go so well:P
popping out of reverse could be a couple of things, but the first thing to try is adjusting the gear shifter.
there are two bolts on the right hand side of the gearchange tunnel under the carpet. theyre in slotted holes so you can loosen them and move the whole assembly forward or back to make all the gears selectable. I cant remember off hand if you need to move it forward or back to engage reverse more, but you should be able to figure it out.
if you still have problems once its adjusted its probably worn gears, but its probably worth checking the linkage under the car just to make sure theres no problem there.
in fact thats probably the first thing you should check:P
