Fuel pump replacement/problem

[Javelin3o4]

I was wondering what all is involved in replacing the fuel pump in my 90 firebird? Does any of the exhaust have to be moved/removed? or do i just drop the gas tank? I cant hear my pump cycle when i turn the key to the on position, and sometimes to get it to start I have to turn the key to the on position, then turn it off...wait a couple seconds, then turn it to the on position then start it. I ran a fuel pressure check and sometimes when the key is turned to the on position it will pressurize to the right psi, then if you turn the key off and release the fuel pressure from the gauge, then turn it on it stays at 0psi until you turn it off then on again