First of all, you made a good choice in engines. I have pretty much gone to OS exclusive after I had a bout of problems with others. In my opinion, they are reliable and consistent performers. If you follow what Big Ed said above, you will have an engine that will last a while. No, don't scrap it as suggested...
it's a great engine.
As far as fuel is concerned, go to your LHS and see what he has on hand. Any good quality nitro fuel designated for aircraft is just fine. I have used several types and brands, all name brands, by the way, (S&W, Bryon, and so on) because they are probably the most consistent in their blending. I started out with 15% nitro content and have had no reason to change. Not that it's better, or worse, it's just what I get and use and it seems to perform just fine.. so if it ain't broke, why fix it.
Big Ed said something that I think should be clarified. 80% oil... well, the blend consists of 80% castor and 20% synthetic... that's not to be confused by a total of about 20% oil in the gallon of fuel which consists of 80% castor and 20% synthetic... or some such blend. The fuel consists of Ethanol, Nitro Methane, and an oil blend. If 15% nitro, then the gallon contains Ethanol blended with 15% nitro-methane, and 20% oil blend. That's if you get 15% nitro. If you get 10% nitro...well, just change the figures. What's important here is to get what is recommended by the engine manufacturer, try it, and adjust it as you feel is necessary. If you have any questions, perhaps it's best to talk to the 'pro' at the field and see what he/she uses and try that.
At the beginning phases of your flying, if you use a good quality fuel, you won't have to worry about it and you can focus on your flying.
As far as props are concerned, go with what is recommended by the plane/engine manufacturer and keep it simple. Once you do, and find that you have the prop you like, then buy about a dozen of them.
CGr