To use mods, you will indeed need to buy the PC version of the game. Most would probably recommend the Steam version for simplicity.
Most of the mods for the games are available either here or at a website called NexusMods ( http://www.nexusmods.com/kotor/? ), but a lot of the older ones would need to be requested in the Mod Requests section of the forums.
As for installing and using the mods, it's a bit circumstantial. At a rough estimate, I'd say 92-95% of mods come with an installer designed by the community for compatibility and patching and the other 5-8% is copying and pasting files to specific spots on your computer so the game recognizes the files. Similarly, 98% of mods come with a read-me and of those, the majority detail how to install them. If you need help, feel free to ask.
And activating the mods in-game? Depends on the mod. Some stuff might need to be done to make a mod activate, some mods might activate through normal gameplay, and some mods might just be running in the background so-to-speak.
(By the way, if you ever want to ask about one of the quotes, feel free to send me a PM)
My personal, made-up quote: "To know is good, but to act is better."
"Words are just words, thoughts thoughts, but actions...actions are progress." - Fair Strides
"Intelligence and respect are all it takes to get along fine. Not a bad trade off, huh?" - EwigD from GameFaqs
"And regarding butchering the language, I have been to the internet. The language is well butchered regularly." - Malkior
"You can either live with the lies or die with the truth. Who would rather lie to live than die for telling the truth?" - Fair Strides