Might want to split the pump and inspect the impeller to make sure it is not clogged up. Just a thought given you do not know the history.
You are probably going to want to Deep Clean your Sand Filter also, but might want to wait until the SLAM process is close to the end.
Unless the sand is clumped so that you can't easily break up the clumps by hand, there is no need, or point, to change the sand.