I own both a Laser and a Sunfish. They are both fun to sail. The Laser is more high performance. Thus the Sunfish is easier to sail for most people. When set up for racing, the Sunfish boom sits lower to the deck so it takes more effort to stay clear when tacking or jibing. The Sunfish also has limited sail adjustments. You mostly just set it for the expected wind and go.
For more: go to the "Forum Jump" and click on Sunfish FAQ's. Read the section titled "How do I Tuna Fish." That will get you started. The best source of info on racing Sunfish, including the above article, can be found in the "Sunfish Bible" which can be bought through the Sunfish Class. See the link also in the Sunfish FAQ's.
I also own a Laser and a Sunfish. One thing you may find out about a Sunfish is that it is much more stable then a Laser, which will mostly work for you, but it can also be a real pain. Then thing is that a Laser, as you may well know, is quite "tippy" and will toss you right out of the boat on a bad tack or death rolls in heavy winds. The SF on the other hand is very forgiving in a blow. BUT once it on its side or all the way over, that very stable platform is again VERY stable and can be a pain in the axx to get back up-right. It seems to me that it is always much more of a scramble to get over the side and onto the dagger board when I loose it on the SF. Whereas for the Laser its just an easy roll over the high side and onto the board when I dump it. Once there, I can just sit and contemplate why it is that I am sailing in so much wind.
Well, just a couple of thoughts here. Let us know how you make out on the racecourse.
Another thing about a sunfish is something called the mast phenomenon. This happens because of the sunfish sail being partially in front of the mast. Because of this the sail is flatter on port tack, then on starbord.