manual trans fluid don't need to be changed ! !
in auto trans the oil is the most essential part, it pushes the converter and generate power to your trans will move your car forward and shift so with no oil auto trans will not work and you have to change it on time because with the time that oil stick to the trans and block the pass of the new oil and make the trans fail
in manual trans the oil is only for lubricate, make gear softly, less sound and kept the trans and gears cool down so you don't have to change it because the oil don't make such an important thing like in auto trans
if you want to change it you can do it but is not so necessary like in auto trans.....Manual transmission changes?
Usually a square ( 4 sided) head pipe plug located near bottom of tranny on side.