Question 1 - can it work OK with some grease missing? 

Question 2 - if it can, is there a way to check it without putting it in the car an running it? Note: There is some resistance to hand turning the fan when it's bolted to the fan clutch.  

Question 3 - does the fact that grease leaked out indicate bad seals and therefore it just has to be replaced? Note: bearings seem fine as I could not feel any looseness on the shaft.

Question 4 - if it does have to be replaced what is the proper replacement? There seems to be a lot of options out there. The car is a 1980 L82 and thus has a auxilliary electric cooling fan (which to my knowledge only came on once, which was 34 years ago after I shut off the car while parked in a field behind a barn following a few miles of darting around country roads at 3 AM for reasons best left unsaid). The fan is 18.5 inch, 5 blades. Original radiator was triple core aluminum (now copper replacement). I've seen options listed for with and without heavy duty cooling but haven't been able to determine if I have heavy duty cooling. The options I've found are GM p/n 88961768 and 14047080. Below is an image of the original fan clutch. 

Thanks for any guidance you can provide.