a 5w40 synthetic will be good, im not sure what your local autoparts store carries but rotella 5w40 synthetic is just fine. Best choice is mobil 1 5w40 but is hard to find so 15w50 is the next best thing mobil 1 offers for diesels.
EDIT: my dads 78 non turbo took in 6quarts. My SD took in 8 and leaked about 2
Fill it up to 6 quarts/liters run the engine a little and check the dipstick, if you need more then put in more. Best if you buy 8 quarts just incase. My 87 takes 8 quarts exactly.