Yes, using a load cell of 700 Ohm is not a problem. For a full bridge measurement, the 9237 is only measuring differential voltage and is thereby independent of the nominal resistance of the strain gauge. The input impedance of the NI 9237 is essentially an open circuit and should not affect the bridge based measurement.
As for the external excitation voltage, there are two versions of the 9237, one with a Dsub connector and one with RJ-50 connectors. You can find the pinout of both connector variants of the device in the NI 9237 Getting Started Guide and the excitation pins for each channel are also noted below:
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