Flywheel alignment 2008 2.5 diesel

[Zoob]

Hello everyone new member from Perth Australia love all the information on here that you never get from a service manual. My brother is the owner of a 2008 Spanish built Nissan Navara 2.5L turbo diesel 4x4 crew cab and now that ive finished working away i will be his mechanic. He recently had a new clutch kit installed by a backyard mechanic who towed the vehicle back to him because he couldnt start it, so being diesel i thought there couldn't be much wrong because diesels run and start fairly simply, I went through the fuel system using a vacuum tool to check for leaks i replaced the diesel primer and few hoses bled the system right up to cracking injector lines while turning over getting all the air out. After getting a service manual and looking into clutch and pressure plate install i see the flywheel needs to go on one way only because the crank angle sensor runs from the flywheel, so i removed the sensor to see if there was any damage, which there was not any visual physical damage, This vehicle just will not start, and was running fine before clutch kit went in. So my question is how can i tell if flywheel is aligned incorrectly without removing gearbox, i dont want to do this to find it is in correctly and i missed something else. I've looked at new clutch kits available in Australia and most seem to have only one dowl pin hole unlike original flywheel that has many so you shouldn't be able to get it wrong we have tried to get in touch with his clutch installer but he won't respond to any questions. I notice crank sensor is just above starter , can I remove it with engine at TDC and see any mark on flywheel? Also would it be easier to remove motor to do clutch than removing gearbox, I see on some forums that torsion bars have to be removed to get gearbox which is twice the size of the engine looks very cumbersome and awkward and heavy and engine removal is usually a fairly simple job. My brother loves this car and is devastated at the minute, so ive gone out on a limb and promised him that I will sort it for him, I noticed a loose bolt on gearbox so his backyard mechanic wasn't trying to do his best work he also changed the front shafts and fuel filter, so i better check those shafts aswell, So if anyone has this issue with the flywheel i would appreciate any info on how you solved it, most importantly how to find out if flywheel is on incorrectly without removing gearbox thank you