Igoumenitsa to Istanbul is a stunning ride; or at least most of it is. If you want to go for it the 1,000km can be done in 1 (long) day of 13 hours BUT it is better to split it into 2 and enjoy the experience.( I normally do it in a day but as this is your first trip out here I would not recommend that approach because otherwise you will be enterinfg Istanbul very tired and given the standard of driving you really need to be sharp).
Igoumenitsa to Ioannina is fantastic. Don't take the trucker road direct from the port but turn left at the port exit, go through the town of Igoumenitsa and then the old road to Ioannina. Stunning mountain passes but watch out if the road is wet!
From Ioannina if you want to site-see take the road to Meteora to visit the mountan-top monasteries; from there pick up the road to Kozani. From Kozani to Veria do not go through the new toll-booths but take the mountain-road to Veria. Absolutely stunning bends and these days no traffic as everyone else is taking the new toll road
At Veria branch off to Vergina if you are into history to see the tomb of Philip of Macedon.
Veria to Thjessaloniki is painless these days but freeway as is most of the route from Thessaloniki to Kavala; however, beware, there are NO service stations so if and when you need fuel you will have to exit the freeway. My recommendation would be to stay overnight in Kavala. Lovely little town. Only, take the freeway to the north of Kavala before dropping into the town; this freeway is absolutely fantastic; it sorts the men from the boys big style with swooping bends and viaducts as it crosses the mountains immediately north of the town.
North of Kavala you can visit the historic city of Philippi!
Kavala to the Turkish border is mostly freeway. It is new and almost empty
The border crossing can be a bit of a nightmare. You will need to purchase a visitor visa (GBP 10.00) and have your vehicle registered on your passport. You will also need to purchase compulsory insurance so make sure you have cash with you as you enter Turkey at Ipsala.
As you pass over the border the road surface will deteriorate massively. Ipsala to Kınala is now all dual carriageway but the road surface is appalling; as is the standard of driving. Beware!! Kınala to Istanbul is now toll road; do not be chaepskate and take the free coast road as this is a nightmare most of the time. the TEM (E80) is much better condition but the driving is manically dangerous. There is no concept of safety distance or even lane discipline. Typically drivers will tailgate you in excess of 160kph and will switch lanes and exit right at the last moment. The closer you get to Istanbul the more manic the driving gets; be prepared to witness some of the worst driving in the whole of Europe. You will need some YTL for the toll payments; but not much. Kınalı to Istanbul is about 2.50 YTL. Crossing the Bosphorus another 3.5 YTL.
Ian
Istanbul
TBH though, once into the 'groove' it was a real hoot 
