change seat unit on minivator 1000 stairlift?

It appears the wheels that run on the track of my (14 year old) Minivator 1000 stair lift are worn and it now tips & feels as if I may slide off! I have an alternative seat unit which could be fitted but the manual indicates that a "feeder track" and a "driver seat toggle loom" are required. presumably to get the old one off and new one on? I rather suspect that getting the old one off would be possible without but can't risk ruining either track or seat. any suggestions?