I am about to start the same project, it's worth a shot !
sand and paint them
If it is "rusted out" you do not repair it, You do replace it with XHCI
Replace them.
Replace
you only replace them if they are damaged or rusted out
If this is an above ground pool you could just pull the old skimmer out cut the rusted section of metal out hit it with some rust converter, replace the section where there is no metal with a new metal forget about the old skimmer setup and replace it with a "floating pool skimmer" they do a better job any way.
there rusted...there bent....there old...you need to replace them
It would be best to replace them with new ones.
If the rust has not eaten all the way through the metal, then in principle it is possible to sand off all the rust, and repaint. But running boards are not that thick, and you probably don't have enough metal left to do this successfully.
Yes, it's possible to replace bbq grill plates on a rusted grill. I think ,if you think quite a few parts that need replacing, its better not to just replace the bbq grill grates. Replace everything. Safety first, right? www.grillgrate.com sells bbq grill grates.
Where's the leak? Wheel cylinder, repair or replace, rusted line, replace, master cylinder, repair or replace.
The engine has to be removed.