How do I change a front engine seal in 2007 Saturn Ion?

I'm not familiar with that car but 1st let's make sure of what is leaking. Did you degrease the entire underside of the car? Then run it when it's completely clean to see exactly where it's coming from, oil has a tendency to follow along parts and gets blown around easily from the wind force and fans and the normal forward momentum of the vehicle. These all make the oil run towards the rear of the car. With that done and you have determined it's engine oil, power steering fluid, transmission fluid or Brake fluid. Keeping in mind that on newer cars these may all look the same, so it's critical to know exactly where they are coming from, since transmission fluid also runs up into your radiator it is also up front along with those others. A cracked brake line would reveal it's self with spongy pedal and low fluid. Power steering can leak for a while and not have any problems till it's gone. Transmission fluid can loose 2 quarts before it'll show any signs of problems but then it's already done the damage.
In most cases as long as it's not engine oil it will be easy to repair.
If it's your front main seal, these tend to be quite tricky, it's usually not only the seal it's self that ends up cracked or worn it can also have a worn area on your crankshaft output where that seal rides. the seals will fit tightly and have pressure against the shaft and it becomes scored, it has a grove worn into it and even a new seal may not solve the problem. I've already done a rear seal on a few GM's and only saw slight decreases in leaks.
Tons of work to get to it and tricky removal and even harder to get the new one in place perfectly. the cost is very cheap to do it yourself. Unless you're removing the engine from the car or it's already out I would think twice before you consider doing it. Figure out how many miles you plan to drive it and figure the cost of oil against the cost of a repair shop doing it, with no guarantee it will work. The proper way to do it is to sleeve the worn crank area when you install the new seal, this means the crank needs to be able to be fully clear and have nothing stopping the installation. The seal will be in 2 pieces so installing it without a sleeve is less work. I would say if you leave the engine in the car you're not likely to do it correctly unless you're pretty good at this type of job. If you have a rack and can stand up under the car would make it easier to do without pulling the motor, laying on your back and trying to do this will be a pain. That's what I did, once I started I wished I would have just left it alone. Buy a manual for your car and see what it has to say about doing this, I think that is the best approach, you can then decide with less than $20 invested. Even if you don't do it, you can always use the book for reference on anything else you encounter. I think I was quoted about $400 back in 1990 for the seal repair so you can figure it's going to be more now.
Good luck on this and Make sure you know exactly what's leaking and from where before you do anything.