A lot of good advice so far in this thread.
Good for you to be so cautious/conscientious. Make sure your fuel
is clean, nothing wrong with pumping a lot of your old fuel
out and then adding it later on when the engine has been running for a while, but either way at least take a sample and give it a visual inspection
. Also before it gets fired up let it spin for a tiny bit to build up oil pressure. Watch the gauge. Another last thing to do is if the valve cover is off take an oil can and give the valve rockers a squirt down. If the valve cover is on still, nothing wrong with taking WD40 or other spray oil can that has a tube and stick the tube in there and give a spray all the way around.
You have also gotten some good advice. Since you are in a spot here is another couple things to try. I am somewhat reserved about suggesting them to a stranger over the internet
as they are what I consider to be improper but both have gotten engines started for me when nothing else worked.
First, is if the front pulley of your engine is somewhat exposed you can see if you can fit a 1/2-3/4 hp electric motor
to the side and use a V belt on the motor
and your front pulley to turn the engine over. If so then letting it spin over for half an hour might free things up. Try it with the injectors out first if they are already out. If they are not out then what the hell, try it with compression
but you may have to help with the starter motor
to get it spinning over first, and depending on the pulleys 1/2 hp may not work with compression
Lastly, if you are totally up the creek and can't do that the last thing I'd try is using 2 batteries and some cables
and jury rig 2 batteries in series and run your starter off 24V. Believe it or not I had an old guy show me this and not only did it get the motor started but the starter motor was fine afterwards and worked for at least a couple years after that when I stopped working on that boat. Just make sure the 24V goes only to the starter and not to the rest of the boat.
Good luck and best wishes to the both of you!