Assuming the store you're going to is a yak store,
then they should have some fisherfolk on hand or
at least some that can give you good suggestions.
Lighting can be had at just about any kayak store,
or over the internet at the various sites like
paddleva.com, austinkayak.com, yakattack.us and
so on.
As for paddles, yes, BB makes a good paddle, and
please, remember to wear your PFD 100% of the time
you are on the water!! Can't stress this enough, and I
know you see a lot of pictures of kayak fishermen on
Google that don't. Don't be that guy. Wear it!
As for rod holders and fish finders, there is a lot to
offer here. But first and foremost, may I suggest you
get out in your new yak and fish it before you start
outfitting it, drilling holes, and so on. You'll get an idea
very quickly of where you want rod holders to be as
opposed to where the manufacturer places them.
And Google is your best friend with DIY stuff. There is
SO much out there.