Wow, thats amazing for your first car.. i remember my audi, what an embarresment
by the way, evan though you detached certain parts of the car, you can re-ATTACH them, and I think thats the best thing you should do, re-attach the different parts (except headlights make that all one group, well atleast when you have other peices to group up)
to do this select one peice, lets say the hood then hit the small box button beside attach, (its in the column with all the buttons :-P), then select the peices you'd like to attach like fender, bumper, ect..
good luck, hopefully you finish it unlike me