If you are taking your own car to Norway, you will need to register for the toll road network in advance. See http://www.autopass.no/en/visitors-payment for further details.
This tour is very feasible in one day, but perhaps even better in two.
Any day is fine, but note that on Sundays, the Norwegian History Centre opens its doors at the relatively late hour of 12:00 p.m. On other days it is earlier, 10:00 a.m. on weekdays and 11:00 a.m. on Saturdays.
It’s better in the summertime. The Norwegian History Centre is fully open from late April to late September only, and during the off-season it is open only on Wednesdays and Sundays. The Viking Farm is open during the summer months only.
A combined ticket for The Norwegian History Centre and Viking Farm is available, saving a little on buying the tickets individually. This cost us 150NOK (€16 or $20) for adults and 50NOK (€5 or $6) for children (Summer 2017 prices).