Might be helpful, some instructions. I replaced my electrical pump a few months ago and it is not too complicated. Bit of a hassle to get it out and the new one in because of a baffle plate in the tank.
My new pump was not a straight fit in the original bracket, so I used two hose clamps to secure it in place. Still works fine.
https://www.skandix.de/en/documents/...-tank/3000438/