Incomplete problem description results in ambiguous or useless answer. At least one unclear point is floating substrate nodes.
Transconductance is a small signal quantity, respectively it's valid for a specific operation point only. Surely v must be connected to a constant voltage, also node I. You'll calculate the device currents and voltages for this operation point, get small signal conductances/impedances and know the answer.
As far as I see, M1 will be in ohmic mode and thus contribute to x node impedance.