Is it possible to use this reclaimed hardwood flooring?
Sanding is best done after the floor is laid. This enables you to get a flat finish across all the boards which would be difficult if not impossible to achieve by sanding prior to installation. If you have any particularly rough boards then you might want to sand them first - but it's not essential.

You should be able to hire a drum sander and an edge sander for a weekend which should give you enough time to complete the job. It will produce a lot of dust so taping plastic sheeting to any doorways will minimise the spread of the dust into the rest of the house.