If you are going to be using multiple mods then yes. But if your not going to use any mods or mods that dont conflict then dont bother
It should already be on when you install it.
You can download all the mods from here aswell as modloader. http://www.minecraftwiki.net/wiki/Mods
Modloader is a soon to be obsolete mod that helps solve mod conflicts, helping you install multiple mods at once.
If You Install Risugami's ModLoader Then All Mods Should Be Compatible With Each Other
Yes, Forge should be completely compatible with modloader.
Yes, to install it you will need modloader, and modloaderMP
The Problem Is That U Need To have ItemSpriteAP So Download That And Install It And It Should Work
Have you installed ModLoader and/or deleted the META-INF folder in the minecraft.jar.
You download it, get the modloader, and install it. Check youtube to see the steps one by one.
Rigusumi's Modloader
Modloader, Modloader MP, and most minecraft mods are completely free. You can download most of them at the Minecraft Forum.
Yes. But you need to do this in good way- first instal forge, then modloader. (or modloader-->forge)