ditto. could require anything from timing-to-engine check, to complete overhaul.
If I were asked to do a conditional, with no logbooks, the first step would be to re-create the logs as best possible, because complete records is a signal part of the inspection process. THEN, we'd start talking about what info wasn't there. The default would have to be that, without contrary evidence, every appliance/ piece had 'timed out', and would require overhaul/ replacement/ whatever.
YMMV - and you might be happy with far less stringent standards - but I wouldn't find it compliant with regs -- or 'safe condition' otherwise.
This is why a unit with no logs has an impacted market price: fixing this is not going to be quick, easy, or inexpensive. And it IS a safety issue.