I've been learning spline modeling for some time but i can'tget the mesh to look right, so i've givin up and am now learning poly moedling which has much better results right away.
There are two very cool links on this site you can use. Under tutorials look for the skyline gtr 34 and also the lamborghini gallardo.
Spline:
Look at the following website for spline modeling tuts and some other very useful stuff.
www.onnovanbraam.com
Also, look at this guys site ; erico nencinni ...or something.
Good luck and let me know if this helps.