What are your interests? Will this be your first time in Scotland? One thing for sure - except for the place names. Scotland is considerably different than Oz!
Your hired car should cost in the area of 200 pounds per week, including tax. That's for a mid size car. A car with automatic transmission would cost a little bit more. Insurance would be extra. Your B&Bs should cost anywhere from 70 to 100 pounds per night. The average should be about 80 pounds. You may want to consider a one way rental, picking up in Edinburgh, and dropping off in Glasgow, as you're travelling counterclockwise. There would be no extra cost.
If you're interested in visiting small towns and villages, there are lots to see along the East Coast. There are some charming fishing villages (Crail, Anstruther, Pittenweem, St. Monans, etc.) along the East Neuk of Fife. St. Andrews is a charming small town, even if you have no interest in golf.
Dundee, although a large city, has some excellent museums, especially around Discovery Point. You can visit them without having to go in to the city proper, as the coast road (A92) skirts most of the city.
Farther north, Arbroath and Montrose are worth visiting. Arbroath for the harbour and the abbey; and Montrose for Bamse the Seadog. North of Montrose are some charming fishing villages (Johnshaven, St. Cyrus, Gourdon, etc.) perched along the North Sea coast. Near Stonehaven are two must sees - Dunnottar Castle and the Fowlsheugh Nature Reserve. For Fowlsheugh, turn off the A92 at the sign for Crawton, and follow the road out to the end. There is a short hike, suitable for old codgers like us (!), out to the end of the path. You'll see (and hear) thousands of seabirds of all kinds perched on the sea cliffs, and if you walk all the way out to the end, past the observation hut, you may see puffins at the entrance to the cave below.
Stonehaven would be a good place for an overnight. There's a small harbour, and several good restaurants.
North of Aberdeen there are several good places for a visit. Slains Castle and the Bullars of Buchan, for starters, and the beach at Newburgh, where you'll see hundreds of seals basking on the banks of the Ythan estuary. If castles interest you, there are many in the Aberdeen area. If you've seen "Local Hero," the village of Pennan, where much of it was filmed, is just up the road on the Moray coast.
I'd recommend getting a copy of the Lonely Planet guide to Scotland. This year's edition is very comprehensive. The Steves' guide gives very little to non-existent coverage of the Northeast.
I hope that gives you something to start with. With only seven to 10 days, you won't be able to see everything, but you can certainly get a good idea of what Scotland is all about.
p.s.: Crikey, how many times did I just describe a place as "charming"? I need to find my thesaurus! It's around here somewhere...
p.p.s.: If you take the A90 north of Aberdeen, and pass the golf course owned by a certain politician of a dubious nature, please give it the one finger salute from me. Thanks!