Hello all, I would like to know if there is a train from Thessaloniki to Kastoria on a daily basis? If so, how long of a ride is it? Are we better off renting a car and doing the drive ourselves? A friend had told me Kastoria is about 5 hours away from Saloniki.

There's no railway station at Kastoria: you'd have to find a bus from Florina or Kozani. The OSE website doesn't list bus connections, though you could try phoning the Kastoria KTEL (0467 22455).

There's also a regular bus service from Thessalonica operated by the Kastoria KTEL We abandoned the attempt to drive to Kastoria, but 5 hours feels about right. Although stretches of the route are high quality, there's a lot of twisty mountain stuff.

Apart from the plane service from Athens (which is supposed to be operated by the appalling Olympic, which means it might operate if the unions can't think of anything better to do, and the management will lie to you whatever the "workers" decide), a hired car from Thessalonica is probably your best option.

There are regular buses between Thessaloniki and Kastoria. Here's the link to find the schedule on the day you are travelling:
http://www.ktel.org/en/timetable.asp
As you can see, it's about a 3 hour drive and there is more than one buss a day.
You could also rent a car for the trip, as driving around this region, with its lovely lakes, is most pleasant.

Incidentally, if you do hire a car, beware of Hertz at Thessalonica airport.

The Hertz staff operate a scam by which they tell you on hiring the car that it's not possible to refuel in the vicinty of the airport. This is a straightforward, copper bottomed, 100% lie.

If you point this out to them, and tell them you'll refuel the car, they'll put the new tank of petrol on your credit card charge (it's virtually impossible to get to see your bill when you return the car to their badly-signed, sloppily managed, return point) anyway.