Welcome aboard Jon.
Do you mean it definitely never had a service until it had reached 24K miles or is that just when the paper work trail starts so it could just be missing some history/service stamps/paper work?
Do you know what age the car was when it had its first service?
By 24K miles according to the Nissan 350Z service schedule it should have already have had a P1, P2 (plus brake fluid) and be on its way to another P1 (plus coolant change) but it does also depend on the age so it could potentially be missing even more?!. E.g. At 1 Year or 9,000 miles (whichever sooner) P1 service
Service schedule here: http://www.350z-uk.com/topic/31110-service-schedule-for-a-350z/
Not sure on the steering rack issue?
Also as long as the car drives well (changes gear smoothly enough etc) then I wouldn't worry about it having had a gearbox rebuild & new clutch, ...in fact I don't think I'll be alone in thinking that is actually a plus point providing it was done correctly by a competent garage.
Guide for new members/potential buyers: http://www.350z-uk.com/topic/22880-guide-for-new-memberspotential-buyers/
Buyers guide: http://www.350z-uk.com/topic/77426-buyers-guide/
Top 100 FAQ's: http://www.350z-uk.com/topic/24796-top-100-faqs-must-read-wip/
Hopefully that helps and take a look around as there are plenty of other useful tips/threads on the forum.