Selecting between 60V source and 1uV measurement
Generically, some series impedance (could be just a resistor) and actively shunt the input to the amplifier with an analog switch, preferably in a way that keeps the output from railing (which should not be too difficult with an instrumentation amplifier since the feedback path does not involve the inputs).
To get microvolt-level error the switch shouldn't leak too much and your amplifier should not have too much bias current relative to the added resistance.  You may well have to use silicon diodes to reduce the maximum voltage the switch sees to a volt or two. That will not unduly affect your signal if it is less than 100mV or so.
If you have trouble getting the desired attenuation in one stage, try two stages with half the series resistance in front of each.
The switch capacitance and series resistance will reduce your bandwidth, but I'm guessing that probably won't be a problem.
Something like this is used for EM measurements in geophysical instrumentation.