Soap up pipe on left side. Loosen fitting and slide pipe forward in to tank. You can then remove pump and access all four duckbills. Don't over tighten duckbills on reassembly
I've always just waited. Shower that gets all the use probably lasts 5-6 years. Other sump that is mostly ac drain just got changed after 20 years. Good idea to keep spare since the design change will require a little more work.
I cut the old tracks far back as I could, just getting under the dash panel. Put a screw in to hold in place and spliced in the new track, also held with screw at splice. Works fine after several years and is not noticeable.
Marty
Find a wider hoist or make a spreader to fit across the top of stainless rails from one side to the other so hull is not pinched. 2x4 I beam 12'-13' long.