Air in the Fuel - additional questions

[FWBennett]

Thanks to John8662 for posting the Tutorial re: Air in the Fuel System.
I still have some questions maybe someone out there can answer.
I've got an '84 Chevy Suburban 6.2L 3/4T 4x4 with an ATS turbo... and an air leak in the system, that's bugger to find - I believe I cured one leak at the intake of the Lift Pump via John8662's method - it stopped surging while driving. My current problem is about hard starting while parked for more than an hour or so - If I park it on a hill nose-down it starts fine - parked level, or nose-up it's a hard start!
So my questions are as follows:
1) Does the ENTIRE fule system need to be enclosed (ie can the leak be in the ruturn lines etc.)?
If the entire system doesn't have to be enclosed - where can I skip testing/looking?
Does the lift pump have a check valve or something to keep the fuel from leaking back to the tank?
What about from the fuel filter to the Injection pump?
The hard to get to hoses (Filler Neck to the tank is original - might the problem be there) does anyone know if there's a soft line from the tank to the main pickup or is it a hard line (and is there an access hole in the back floor or do you have to drop the tank?)
Thank you all for the help that you offer!

[Liftgate]

To answer some of your questions, the filler neck hose to the tank isn't a problem with air getting in. I have an 84 GMC 3/4 ton 2x4 suburban with a 6.5 L non-tubo engine. I had a bad fuel tank sending unit and had to drop the tank. Ouch. I have the big 40 gallon tank and it was about half full! There was no drain plug either so I had to siphon it out. From the sending unit into the tank, the line is steel. From the sending unit to the frame, the lines are rubber. There is one suction and one return line. The suction line could be leaking and letting air into the system. From the frame rails to the lift pump, the lines are steel. Then they change to rubber at the lift pump. At the outlet of the lift pump, the fuel is pressurized to the fuel filter assembly and then to the pump. If there are fuel leaks there, you will see them as wet places or dirt if they have been there a while cuz the fuel will attract dirt. Check to see if the injection pump is leaking too. Mine was leaking bad and had never been replaced/rebuilt. That could cause problems too. Parking uphill/downhill is a clue but not sure why. Hope this helps some :)