Convert 0-5V from DAC into +/-5V?
Assuming the galvo amplifier has a relatively high impedance input (doesn't draw more than a few mA) you can use this circuit:-







simulate this circuit &ndash; Schematic created using CircuitLab

The amplifier has a gain of -2 from the DAC output, and D1/R2 biases the voltage at +5V out with 0V in, so the output will change from +5V with 0V in to -5V at 5V in. R4 provides some vias current for D1, which is the -5V reference to offset the amplifier. 

If you want to avoid D1 and have a 5V reference already, you can use the remaining amplifier to get -5V from the +5V reference as shown in the dashed box.