The nut is down by the floor, you pull of the panels above the pedals to gain access if this is lose the wheel will be jiggle but it will not cause play in the rack as the shaft is splined together.
The guibo is easiest to check from underneath, but you can grab it from above by reaching down around the powersteering fluid and mastercylinder. Grab both sides and try to twist, there shouldn't be play but it can deflect under pressure held together by large rivets
I would consider jacking the car up, locking the steering wheel and checking for play. If anything is really lose it should be felt as vibration, not just loseness.