...can you still lower the landing gear or landing gears by hand or does the engine have to be running to do this?
The landing gear system on a Lockheed 10 is electric. There is no manual retraction or extension system.
Thought there was an emergency hand-crank for extending the gear.
There should be no reason to use it if the engines quit, so long as the battery was in good shape - the electrical extension system ought to work fine.
As to the scenario of losing both engines, then a landing necessarily being harder than normal - maybe, but the only reason would be dealing with a compressed workload. If there's time to get the wheels down, there's time to settle the bird normally. So I don't see a hard landing as a 'necessarily so' outcome in such an event.
Also, had the engines flamed out prior to landing, presuming fuel exhaustion, then we'd not have certain other things that logically go with a landing on Niku - subsequent radio transmissions for several days, etc. Plus some of us remain with the belief that there was enough fuel to get to Niku and broadcast for a time.
Not sayin' a dead-stick couldn't have been the case, just sayin' it would be a hell of a coinkydink.