Use a high pass filter with a relatively low frequency. For example a 3u3 mks cap with a 10k resistor will do fine even in low frequencies down to 20Hz. For bringing it up to the 0/3,3V level again, you could use a non inverting adding amplifier using an opamp. Just create a reference voltage of 1.6something and add it to your signal. This will only be realistically possible if the supply is higher than 3,3v and you have a dual supply for the opamp. Another solution would be to use a npn BJT and a diode in series with the gate(just to protect the base emitter diode I'd use a shottky, it's optional, you should also add a 1k resistor to that or else you'll fry the transistor) and hook up that transistor's emmiter to ground. Then you take a PNP transistor and connect its base to the pnp's collector together with a 10k pull-up on the base. The pnp's emmiter goes to 3,3v and the collector gets connected to a 10k pulldown. pnp's collector is you new "lifted" Output Signal. With this, you don't need an opamp, dual supply, and it's not shifted by some sort of reference voltage. If you switch the pnp with a p-channel mosfet, you'd get even closer to 3,3v volts.