I tried both your suggestions and neither worked.
The first laying machine on side and working from beneath is no good as you can not onto the fixings to release pump from filter housing and even if you could and seperate the two sections ie pump and filter housing you would not be able to re-seat the new " O " and re secure the two components to create a water tight seal.
The second option only allows you to release the electrical spade terminals and get onto one of the fixings of the pump the work space is very limited due to the location the pipes and and emergency emptying hose you cant even get onto the release clips which are a combination of spring type and dubilee type. I have now sorted it . you have to remove the rear section remove two hidden fixings which hold the front panel.
refit the rear panel and fixings to support the metal top frame to which
the drum springs attach
Remove top facia panel
Pack inside with towels and card board to support / stabalise drum
Remove front panel after first removing spring to release door rubber
and door latch screws release door latch unit
Lay machine down and release plastic fixings from underside of machine which then releases pump and filter housing as a complete unit .
After first releasing all pipe connections and electrical tabs .
New pump now fitted to filter housing water tested and reinstalled machine back together and working
With respect your suggestions were unsuccessful
As you can see from my notes my method was .