Put Mercon V in it and forget the lubegard, the lubegard makes cheap Mercon 3 work like Mercon 5 then again might not.
Yes 12 qts down the filler neck, start it up at 6 or 7 qts and start checking the level at 10, it can be tricky to check because fluid from the tube will get on some of the indicator. Look for full around the indicator coverage for a more accurate reading. Fluid should be checked idling in park.