I would urge you to have your system professionally designed. There are many, many pitfalls that you can encounter that will make your current questions seem trivial. What you need to have is a good scale drawing of your property, including buildings, driveways, water source, and etc.. Then find an irrigation company in your area. They have designers on staff that know how to design a system that will work right. I don't know about every company's policies, but when I had my yard system designed a lot of years ago, they designed it for nothing! The only requirement was I had to buy all of my supplies from them. Their prices were about the same as the Big Box Store, but the quality of the sprinklers was better. Most of them are still working after 24 seasons. I did my own trenching with a Ditch Witch and planted the PVC pipe and sprinklers myself, but you might very well find their labor costs to be so reasonable that you won't want to mess with the work yourself. At least get the design done even if they charge you, you'll be money ahead I promise you.