FYI, there is a TDC mark on the crank pulley.
The engine's computer electronically controls the ignition timing (electronic adjustment of the rotor on the distributor). So no, you cannot adjust the ignition timing of the engine; it is constantly adjusted as the computer sees fit. You can rotate the dist housing and not adjust the ignition timing.
However, by rotating the distributor housing you are adjusting the 'cam retard' timing. This is the correlation between the camshaft and the distributor. This must be set +-2* TDC or you will get a check engine light (code 1342 if I remember correctly, I don't have my book with me). To adjust the cam-dist correlation you will need a special scan tool to read the setting. Cheapest one I've seen is over $500 so just haul it to the shop. I got mine set for $60.