As far as I am aware there is no ferry from Greece to Turkey. There used to be a ferry from Ancona to Turkey but that ceased sailing a few years back. We regularly drive across Europe to and from the UK, and holidayspots. The best route, though not the cheapest, is UK-France-Belgium-Germany-Austria-Italy- Ferry to Igouminister in Greece from either Venice or Ancona-Then overland to Turkey crossing the border at Ipsala. Then Ipsala-Canakale-Izmir-Fethiye.
There are no tolls in Belgium, Germany or Austria (no tolls on the short bit of road from Calais to Belgium either) Austria you will have to buy a Vignette, usually from a garage near the border, its about 9 Euro's. Then depending on your route, some of the tunnels in Austria have tolls on them too, again around 9 Euro's. There are tolls on the Italian motorways, you can pay cash (Euro's) or credit/debit card. There are tolls on the motorway linking Igouminister and Ipsala in Greece. Its around 20 Euro's in total to cross Greece. Watch out for the junction at Thesseloniki, if you have not done it before it can be tricky so keep your eye's peeled. Not as bad as spaghetti junction though. There is a toll on the motorway from Izmir to Ayden. You need a pre paid sticker on your windscreen. These can be bought at an office to the right of the toll gates or at the 1st services on the dual carraigeway when you leave Izmir, about 10 k outside.
Unless your hire van green card insurance covers Turkey (most of them don't) you will need to buy insurance for the van at the Turkish border. Also be aware that if you have any electrical goods capable of receiving a TV signal you will have to pay a banderol tax on it. Any mobile phones brought in will have to be registered at the tax office in Fethiye within 30 days of you entering Turkey. But I'm sure you know those bits.
Good luck, we did the drive over in 2007 when we moved here and enjoyed the journey.