The only temperature limit given in the manufacturer's info is 200°C for the end "sleeve" where the lead wires are fastened. The sheath is steel, with MgO insulation. The heater wire is Ni or perhaps a Ni alloy like nichrome, so all the parts are pretty good for high temperature. As long as the "sleeve" end of the heater is outside the cell, the sheath should be OK up to 500°C at least. I suspect that could be easily exceeded in vacuum, so conservative application of power will be needed during the bake-out. Start low and beware of the long thermal time constant of the cell, while watching the outer surface temperature.
Regarding the power supply, I'm using a HP/Agilent 6555a, which has fully isolated output and both current and voltage limiting. It's an old-school analog supply, so lower risk of the residual output noise often seen from a switching supply.