Ok. Glad you got it sorted. It's always nice to know if the advice has been useful. :)
One thing I forgot to mention is that you'll find you need to fill the old fixing holes in the deck and drill new ones for the Perko. I used Plastic Padding Gelcoat Filler and after dressing down and buffing with Farécla cutting paste they couldn't be seen. An alternative I've seen done is to make a wooden mounting pad a similar shape to the old lamp. The Perko comes with flying leads so you'll need to splice them to the existing cables and push them down the hole. I used crimp splices for this as they are slim enough to pass through.
With regard to the toe rails I'm finding my varnish only lasts for two or three seasons even though I've used International's 2-pack clear primer and up to 6 coats of varnish. I'm toying with the idea of replacing them with PVC (that'll make the purists howl!), either brown or possibly white. I'm definitely going off the idea of external wood on a boat!