A lot is going to depend on your style of shooting honestly.
Sights are too much of a pain when bowfishing. At first you'll probably aim down the arrow, but it will get to a point where it becomes instinctive if you stay with it.
I shoot fingers, a few people use a release, that's you're call. If you decide to shoot fingers it is wise to pick up a set of No-gloves or Bowfingers. Shooting fingers allows you the advantage of not having a hand stuck to the string. I would never be able to use a release because I am always driving the trolling motor with one hand.
If it is a hunting bow I would assume you have it set between 60-70 lbs. My advice would be to turn it down as low as it can go while being safe. I shoot at 35lbs and STILL will shoot through a fish on occasion. Also, if you miss, the arrow won't be stuck in the bottom as far. Also keep in mind, unlike deer hunting, you will be drawing your bow dozens of times. Your shoulder will thank you!
Your hunting rest probably won't work well with the heavier arrows. Roller rests are ok, but I would highly recommend something like the Muzzy Fish Hook. It prevents the arrow falling off the string and gives you more adjustment. Very rarely do you have time to have perfect form. The exception would be if you are using a whisker biscuit right now. It will work if you put some glue on the bottom bristles to stiffen them up.
Reels are your call once again. The drum reels are a great inexpensive way to get started. The AMS Retrievers are basically foolproof and mount in the sight holes on your riser. You can also get a reel seat and set up a spincast with some heavy braid on the stabilizer hole.
Arrows are 5/16" fiberglass. There are a ton of points you can choose from. A couple that I would consider are the Muzzy carp tips, or Innerlock Pro Points. Both are very good and around $7 a piece.
Please make sure you use safety slides or rings, You do not want that arrow coming back at you!
The two best places online are Backwater Bowfishing or Bowfishing Extreme. Both have very good customer service and the owners are very active in the sport themselves.