I just installed the remote start in my 2010 in October.
Are you going to be installing an aftermarket system or the Ford OEM kit? Tasca is being flaky with compatibility -- it shows the OEM systems when you select 2007, but none of them show up in the applications list.
I know on at least 2009 and newer, the wires you will need have been set aside to aid in installation. The wires you need to access (horn, dome lamps, brakes, door locks, parking lamps) all have an extra six inches or so, taped aside in easy-to-reach locations.
Here's the instructions for the 2010 model year -- everything should be similar on your car, with Fusion instructions beginning on page 45
Even if you're using an aftermarket, this should help you locate important wires. I cannot guarantee that the 2007 has the extra slack / identifying tape, however. Also, I never put in the hood safety switch. I'm not comfortable drilling into my hood, I didn't want to fish a wire through the firewall, and the damn thing is a fail-unsafe system anyway. It'll close the circuit when the hood is open. With that design, a broken wire or simply not connecting the wire in the first place
will make the remote start think everything is fine.
And putting the antennae where they recommend just ugly and stupid. I tucked it into the edge of the rearview mirror right at the headliner and it'll still work from 2½ blocks away.
I'm also planning a writeup on how I used an Arduino to activate my heated seats / defrost with the OEM remote start.