oil leaks

[nickz84]

my 79 gmc the engine is a 72 or 73 400sb i believe engine is leaking oil from 2 places and i havent got any idea where to begin one leak is coming from where the pulley to the belts are in the area right above the frame in the front it leaks right onto the frame and puddles up and the other is farther back closer to the oil pan and transmission pan,it actaully drips off 2 metal tubes that run into something next to the trans pan. i bought the truck from my dad 2 years ago he had oil pan gaskets and front and rear seals changed and someone told me today that they may need to be replaced again is that possible already.any help is appreciated im totally new to the gmc/chevy thing so any help is appreciated..also how do i locate the numbers to identify what year the engine is i dont know where to look or what to look for thanks again