A Minecraft fan group!
To buy the game visit there offical site at Minecraft.net
I'll show you, what is needed to install the High-D Texture Pack (all versions).
Minecraft Coder Pack Set Up for 1.2.5 and Up, Part 1 of 3, By Fyoface
This is an easy way i use to install a minecraft mod such as "Toomanyitems" for windows.
(You will need WinRAR or 7-Zip, i believe they are free)
How to mod minecraft forge mods
This will help you with all your needs
NOTE: Information extracted from internet, not mine.