Rolex got you going in the right direction. First source of info should be the owner's manual for your car. In there they should outline pretty well a routine for breaking in the engine. That is step one. Then you can get to the task of fine tuning your engine to run best where you live. There are a few rules to work by. You asked about high heat environments. You shouldn't have to worry too much about temps in general. Just make sure you tune the engine to account for it. Generally, the leaner you set the mix, the hotter the engine will run. BUT, when it's hot outside, you have to LEAN the needles. Seems backwards, right? But when it's hot, the air is thinner. That basically richens your mix. Because there's less air to the same volume of fuel. So you have to cut the fuel mix a bit. Engine temps should still be fine. If you're worried, pick up an infrared temp gun to help. That way you'll know how the engine is running.
Rolex is right on a second count. You found RCNT. A great place for info. When you're just starting out, there are tons of questions. Most of which have either already been addressed here. Or at least experienced by someone on the site. I usually start by using the Search function just to see if the topic has already been asked. If so, read up. Then if there is any other info you need, just ask away....
Fuel is a topic with a fair amount of leeway. Make sure you're getting fuel specifically formulated for car engines. These usually have a fair amount of oil to keep the engine lubed and cooled. What %? Well, that's a debate. I think you'll see most use around 20% nitro. But it depends on what works best for you. I use Byron's Race 2500 25% nitro.
And as far as getting stuff online...well again a question with alot of answers. Best bet is to support your local hobby shop if you have one. It's always nice to get personal attention. But if you don't have the luxury of one, Tower Hobbies and Hobby People tend to be popular online. But there are many many more of which alot of us have had good dealings with.