i have a 72 and did what you are doing
and i replaced the screws and i used silicone under the wood..make sure you seal around the wood so no water makes it under the wood even tho you will have some kind of sealant under there. just like you would on a window or tub, spread some sealant around the edges...my rails looked like driftwood when i first bought the boat, but a lot of sanding and lots of polyurethane took care of them..they were cracked and a mahvelous gray color when i started, but after finishing them up.. the look grrrreat, again.. i emphasize the words, a lot of sanding..and yes i also had to be careful when replacing them as they do have a slight curve in them.Just make a dry run before placing any silicone under them and line up all screws to see if it's ready to go..as far as the windows.. i believe catalina direct sells a kit to replace "da stuff" around the windows... good luck.. tom