i dunno if an NA skyline will really be a HUGE step ahead of the commodore as an overall package.
a GTS-t would be a much better option i think.
are you on Ps? if so, i would wait until you get your full licence, then get into a nice clean GTS-t
although i have not driven an NA skyline, i did own a VP commodore, slammed, rims, with big audio etc. very happy with my upgrade
good luck