Don't know of any guides. But you will be limited to sea trout fishing if you are going that early. Some lakes open up for fishing around April 15 but don't think you want to do that. Most trout fishing does not really get going until late May at the earliest and is really only good over the summer. The sea trout fishing is for fish that are going back out to sea kelts or spawned out fish. The sea trout run the rivers in the Fall spawn and over winter in the rivers and then go back out in the early spring. Just wanted to make you aware of that. Good luck with only one day you will be limited to try something somewhat close to Reykjavik I would imagine.