If you've never done your own work, I wouldn't recommend the first two as your first venture. You should make your own call, of course. The third sounds fishy and I wouldn't address it at all without a clearer understanding of what they're trying to sell you.
Just from looking these items over, they look like scheduled maintenance. Those types of tasks are usually not terribly complex but they do involve some time commitment to properly complete and clean up.
My recommendation is that you get to the point where you're changing your own oil (and disposing of the used oil properly) before tackling slightly more complex tasks:
Power steering flush: here's a Focus forum recommending a straightforward procedure for the flush. It's not terribly hard but you now have a quantity of dirty power steering fluid that you need to dispose of. It doesn't go in the trash or down the drain. Decide whether that's worth the hassle.
Fuel filter replacement: again, the procedure isn't terribly complex. Here's a quick and reasonably good quality video. Note that he's doing his best to reduce the pressure in the system by cranking the engine over: if you don't do that, there's a good chance that you'll cover yourself with a fine mist of gasoline. Don't do that.
Lower Intake Decarbon Service: Okay, I lost my mind before. I have heard about carbon build up but only in the context of direct injection engines (not relevant to the cars at my house). It's not clear whether the 2007 Ford Focus could have one of the direct injection Duratecs. If it does, I would talk to Focus owners first and find out whether carbon build-up is a problem for your engine. If not, carbon build-up is generally considered to be a non-problem for fuel-injection cars using quality fuel. I vote a provisional no.
In the end, even if you tell the dealer yes, yes and no on those three tasks, I've saved you about 50% of what they were asking. Maybe you should consider having Santa bring you $200 worth of tools....
