Hzrd280zx

im about to buy my 280zx....what should i look out for. there are a coupe of dodgy tings but my auto elec mate can sort that out. the engine isnt stock, cause its not a carbi...its a skyline engine i think (an old one) its go brown kinda flaky $^!# on it.... what should i be looking out for, the interior/exterior looks great, engine sunds good...but i dont wanna split a head gasget or sum $^!# and be carless..... please help....