You will find probably find that the speed change mechanism is gummed up with dried grease. It should operate easily and without much effort (unlike the conquest)
It should be removed for cleaning and regreasing.
The other levers depicted in the picture have to come out in order to get the speed change mechanism out so take plenty of pictures and notes to assist you with reassembling, or you could do it by leaving it in situ and cleaning/regreassing that way.
Check that the speed change operates smoothly and without too much effort.