Don't know where the fill/drain plug are in this application so could be on the end of the 'box and accessible through the wheelarch or you might need to be underneath the car to do it.basically you get things up to operating temperature then with the car level gearbox in park and engine running you remove fill plug and then[as you say]there should be a slight weep if it's up to level.
Had a MkII back in the '80's albeit the paupers 2 litre Pinto engined job :'( Still a nice car though.Always thought the MkI was best looking of the Granadas-especially the coupe but then pretty much anything pre-kermit Scorpio looked decent-even the MkIV Zephyr/Zodiac
As there's no need to leave because you no longer have an Omega (th is place would be empty if you did!)then keep posting (you're now showing 242 so only another 8 to go)as surely someone on here will be interested in the parts you have.
People often say us Yorkshire folk[yes I know I live in Lincolnshire at present but I was born in the West Riding of Yorkshire]are tight. I'd say we're not tight at all just careful wi us brass