Hi Daz, Is your skyline an R33 or R32? are you southside or norhtside?
most on here could tell you the bolt on mods from sight
and yes, it would be good to know what the seller advertised.
most list there mods but if they didn't I'm sure some one could help.
pics of engine bay (multiple angles, and the turbo), dash, and underneath at the exhaust and inside wheel arches.
wont be able to tell about the engine internals from external.
Remove passenger side kick panel and there will be an ECU - take a pic.
[Edit] - oh and I wouldn't buy another one just yet. Skylines have a way of draining your money