AntoineLafontaine had it right above. You can type in:
/any_number_of_wrong_paths /install.php
and get the response 'No Input File Specified', since that comes from the server, and not the install.php itself.
I made the fatal assumption that 'No input file specified' was coming from the install.php rather than the server, which kept me searching for another problem, including messing with the install.php code.
After that tweak it started working not due to my changes to the code, but the fact i got the path right that time around. My second problem of 'No Direct Script Access' was simply a result of me messing with the install script and creating a new problem for myself.
Lessons Learned:
(1) always check your path
(2) 'no input file specified' comes from the server, not the script
(3) don't take the engine apart before checking to see if you have any gas