Old style Bennett type tabs take a hydraulic pump and they're expensive to replace.
http://www.bennetttrimtabs.com/partprice.htm
They make a new sealed electric unit that might work for you too, but I don't have any experience with how long they last.
As for the splash rails, much of the hardware was bolted from the inside of the boat, requiring access from inside through the headliner or from behind paneling, etc. It may be easier to attack the fastener from outside. I have had to drill many out.
James