You'll need to find the schematics and board views to figure out where you can tap the power. You still need to have a means to connect the USB signals.
I really don't see this as that workable as much as you want a built-in IR receiver without doing significant physical damage to your system to fit things in. Don’t forget you still may need to get your system fixed or you will want to sell your system at some point. Most people won’t appreciate the mod’ing you’ve done so it won’t get top dollar it could.