I saw on many sites of these mini universal TV remotes that only need you to press on the mute button until the TV mutes and then you can use the remote well, I wanna build one of those to so, can the expertise of this site help me? Perhaps some schematics or diagrams?
The schematic is simple - micro-controller, transistor driver, and an IR LED.
But it's the software that is difficult!, you first need to obtain the codes for thousands of different remotes, them devise a scheme to store them in very little memory - the actual transmission part is trivial (check my PIC tutorial on Sony IR remotes).
Buy one from a cheep store, if you want to lear how it works take it to pieces and look at the output with an oscillosope as you press different buttons. It'll probably cost you more to build than it would to buy.