Hi mate, the obvious pointers for making it more sporty are fitting ST parts... front and rear bumpers, side skirts, spoiler, 18 inch alloys, they'd all make a difference. You can lower then as well for a more 'agressive' stance. If you didn't wanna go the ST route, you could get a CC front bumper, or you could get an MS Design lip kit which come up every now and again on ebay and different Ford and Focus forums/fora.
With your car being black also you may get lucky in searching for ST parts and find ones in black which aren't in need of a respray and could be fitted as is.
Another option would be to just have your current black plastics colour coded. I hate the standard plastics trims on the bumper inserts and lower valances, but colour coding the bumper plastics and standard spoiler makes it look a lot sharper.
Here's a pic of my Titanium, with main exterior mods being lowered 40mm and sitting on genuine Focus ST 18s (see my sig below for a more comprehensive list - MS spoiler, black ST xenons etc). It's having an ST kit fitted as we speak though, so should look a lot 'sportier' this time tomorrow!
As for performance mods, I wouldn't be too sure on the petrol. In my TDCi the most popular options are exhaust, uprated intercooler and remap, but pretty clueless on the petrols sorry.
As for the climate controls, I've heard/read it's a massively involved job to do the switch. It's somethin that crossed my mind when I first got my Focus, but was quickly put off the idea after a little bit of research! Will see if I can find any reading for you...