PIC16 LP drive level - do I need a damping resistor?
The effective output resistance of the internal cmos gates has not been stated .So I suggest you leave provision for the output resistor .Remember that a resistor has much better tolerances than the internal gates .If you are doing a big prod run the validity of getting it right is great .If you do overdrive the Xtal you could blow it up like you said ,I havnt managed this on 3V3 .You could get lousey accuracy ,3rd overtone operation which will really screw things up.More subtle you could get unreliable starting because the osc needs some of the phase shift produced by C2 and the total effective resistance .If you are a bit worried about all this then check the osc waveform on a scope .Too much feedback tends to square things up and too little makes the sinewave too perfect.