I checked a number of my Selectrics and all were rated at 115 volts at 1.3 amps. If you were to use a North American manufactured Selectric you would need a voltage transformer (converter), and one that was rated for the load (I wouldn't use the bare minimum as there could be a higher current draw on the motor start-up).
Something else to keep in mind is that they are quite heavy, and shipping could become an issue if the person sending it doesn't pack the machine correctly. The cost of the shipping would also be substantial.
IBM manufactured Selectrics in a number of European countries - Belgium included (factory code = 2), so if I was in your shoes I wouldn't consider buying one from North America and would do everything possible to source one locally.
I can't speak about who might be able to service your Selectric in your area, but they are more complex machines than manual typewriters (to work on). In my area there are very few who can service these machines today, and that despite the fact they were manufactured here.