It has oil seepage at areas of cylinder head, thats not the greatest sign, also fluid leaks at areas of power steering pump can't comment too much but it isn't a good sign it's got wet oil in engine intake and the engine is misfiring.
RACQ are good, but a performance shop would know alot more ..but hey, it's up to you but if I knew it had problems like that - i'd stay away and shop around. I know you want a Skyline now, but better you find something in better condition.
Have a look at the For Sale section on this website, some good buys there.