Plastic vent thing on 5-speed??

[Daniel Neuman <dneuman@stars.sfsu.edu>]

Hello All,

        I was degunking my 5-speed transmission yesterday and this little 
plastic vent lookingn thing broke off from the top side of the case?? I have
no idea what it is but when I put the transmission on its side oil came out of
the hole?? What was it?? Does it have to be replaced?? How do I replace it??
                Thanks,
                        Daniel 69 2000