PIC18 with ACT HC49/US XTAL
You seem to be mixing up several things.  You state that the datasheet says a resistor should be used, but even the section you quote only says "may be required" for some crystals.  Then they go on to talk about overdriving resonators, not crystals.

Basically, I wouldn't worry about it.  Use the lowest power oscillator setting that results in reliable operation.  If you do that, you're quite unlikely to overdrive a ordinary crystal.  Take a look at the output of the crystal on a scope, but remember to use a high impedance scope probe.  A "1x" (usually 1 M&Omega;) can kill the signal. Use "10x" or 10 M&Omega; at least.  If the resulting sine wave on the ouput of the crystal is nearly the full supply range, then you probably want the next lower power setting.  Up to about half the supply range peak to peak should be fine for ordinary crystals.

No, you can't tell the crystal "cut" from the can shape.  Sometimes the datasheet mentions this, sometimes it doesn't.  It is probably better if you don't think you know something about the crystal based on its supposed cut type anyway.  The important spec is the power level it can operate at.  Physically bigger crystals will work at higher power levels.