apparently you have a draw or a short when the vehicle is shut off, disconnect the battery when not in use and see if the battery stays charged.
50-450 usd
50 cents. They are in common circulation.
The US did not have a non-denominated stamp in 1973. The first one was issued in 1975 for Christmas.
10w30 will probably work fine. If it doesn't get too cold a 15w40 diesel rated oil will probably be better.