1996 Lincoln Continental Battery drains overnight

Bought this car used as is & I was told it would only backup & not go froward.
After running a PC based scan I got no errors.
I had it delivered with a roll back truck & just assumed it wouldn't move forward.
I finialy pulled it into drive & drove it down the driveway & backed it up, no problem so I checked the transmission dipstick & the fluid was black like oil, when I changed it about 11 quarts came out - wow !
Also all the bolts made a snapping sound when I took each one out, like the fluid & filter had NEVER been changed ( I believe).
Now my main problem is that the battery goes dead overnight & I've put a couple in there just to make sure it's not the battery. The ac/heat fan. Would not work & the wipers were stuck in the half way up position & they don't work either. I saw a plug on the wiper motor so I unplugged it & the ac/heat & fan started working just fine but it still goes dead. Also before the interior lights would not turn off, now they do & I didn't mention that the power windows don't work & door glass fell into door on drivers door. I also unplugged the unit that operates the power windows just to see if that was part of the problem & before I unplugged the wiper motor the red battery indicator would light up when idling, after it never comes on.
Was wondering if maybe a different code reader could shed some light on the problem(s).