The Northstar would never fit in a Saturn. That motor only bolts up to the 4T80E trans which fits the large GM FWD platform, plus it is likley too large to fit inbetween the struts of your Saturn.
There are better choices for a motor swap out there, like a supercharged 3800, or even the new Eccotec motor coming out in the new saturn, and standard in the L sedan. That new 4 cyl is engineered for serious power potential, as the stock longblock can handle over 350 hp.
For a first car, even the stock 1.9 motor may have some power potential. Walk before you run grasshopper.