Conduct a proper game inspection and diagnostic checks, just like any used game as you have done before, and how operators have done for decades.
The process is identical, no shortcutting.
Inhale the "NIB smell" as you go (I should bottle this and sell it).
Avoid the new generation owner methodology:
1 ) Put legs on (especially w/o a proper dolley)
2 ) Drop balls in game
3 ) Turn power switch on
Expect the unexpected, and research the title for typical service bulletin updates in old stock games that were not updated.