It pays to know your PEOPLE Magazine. Last night on “Who Wants to Be a Millionaire,” contestant Dan Blonsky, a single, 34-year-old attorney from Miami, took home the full seven-figure prize. His final answer to the final question concerned the distance from the earth to the sun (93 million miles). But his $500,000 lead-in question concerned the identity of the first celebrity to appear on the very first issue of PEOPLE Magazine, in 1974. (Answer: Mia Farrow.) By the way, No. 1 rated “Millionaire” filled all but three of the top 10 spots in last week’s Nielsen rankings. “ER” was No. 4, the new Fox sitcom “Malcolm in the Middle” was No. 8, and “Friends” was No. 10.