I drew a little picture to explain what you should (or what I usually do).
And yeah, you should try to finish it. But take your time, do a lot of tweaking to each part until your rather satisfied with it. Only then move on to the next part. And I hope you really like the car you're modeling, because that is, imho, the key to being able to finish a project. If you don't really like what you're modeling you'll probably lose interest (unless you're being paid for modeling that is, of course
).