I would cook it at 350F unless stated otherwise. That's basically "normal". It's done when it stops being translucent in the middle. Plan at least 10 minutes per inch of thickness. If you don't want to pull it apart with a fork to see if it's done, you can run a metal skewer into the thickest part from the side, leave it there a few seconds, pull it out and touch it to your lip. If it's cold, it needs more cooking. That was an Eric Ripert tip, and I'd say he knows how to cook fish.
I probably would chop them moderately fine. I don't imagine you want big hunks, but you probably still want to notice they are there and get a little crunch out of them.
Have you ever wrapped a fish like that in potato and pan-roasted it? Peel the potatoes, then slice them into thin layers with a mandoline. Lay out the potato pieces in an overlapping pattern, put the fish in it, then roll it up, sort of like making a sushi roll. Then fry it in a pan with butter and oil until crisp, flip it, put it in the oven until done. It helps if you lay out the potato on saran wrap, so you have something to help you keep it all together (like the bamboo mat does when making sushi).