How do the mods work? After i install them within the main game, can i still play in any server or it has to be a modded server? Also, can i play the original game afterwards or i have to reinstall the whole game again?

Doesn't Steam put the mods in order automatically?

Thanks for the server settings and the mod pack order list.
My Internet connection has been flaky in the past so It's single player for me.....