New to repair (Need guidance for control valve kits)

Hi guys very newbie in repair of machines here *** Need some guidance for control valve kits repair and main pump kits. I understand that buying the seal kits packed by people is very very expensive, therefore i am determine to learn to pack it myself by looking @ parts book and buy the invidiual orings itself. However guys i need help in some of the things here. I have a machine for Hitachi Ex200-5 but but !! when i kit the machines myself its so different with the content which i bought from the market. Why is that so? Anyone knows how the kit is reference from? Lets say for control valve kit, 1. It consist of the Valve;control 1 - 5 2. Main pippings (1-4); under upperstructure 3. And is pilot pippings included inside also? Guys help me.. cracking my brain in office like 20hrs a day for this thingy..