Merhaba! (Hello) - we just came back from Turkey about two weeks ago. We have been many times, its such a lovely country. Where are you going? This time we went to Dalyan, which was fabulous.
First of all money - better rates out there than here, plus they will accept sterling and euros, and you can just draw TL out of the cash machines too. I wouldn't bother with dollars, imho. Were it me I'd probably change a few quid up so that you've got some ready money, and either take the rest as sterling and change it there or just draw it out of the bank. Do NOT, whatever you do, change either at Gatwick or Dalaman airport - terrible rate and fees high.
Food. Turkish food is in my opinion one of the nicest cuisines in the world. Lots of good stuff for low carbing - grilled meats, chicken, seafood etc. There are also quite a few sort of casserole things - guvec - fish, seafood, lamb, chicken. You can always get 'touristy' food eg pizza, egg and chips, but have to say we don't bother!
Starters can be 'meze' style where you have small dishes shared between you, or more substantial things eg one night I had the best prawns I've ever had - just described as 'garlic prawns' on the menu, they were the size of small lobsters, so fresh, beautiful.
I'd probably avoid Borek (cheese pastries, fried) but things like aubergine salad or antep ezme (chilli/tomato salad - hot) are lovely and not too horrible on the fat/carb front. Lots of different cold veggie starters available. Vine leaves are nice, and my absolute favourite is stuffed aubergine.
Adana (I guess this is what translates to Doner) is spicy minced meat in a kebab style - mine came with piles of salad, and you could ignore the wrap that comes with it. Kofte - meatballs - very nice. We also (strangely) had a couple of very good steaks in dalyan - plain grilled fillet, beautiful.
I could go on about this for hours but fear it is turning into a bit of a food porn type thing!
Puddings - they're not big on puddings, preferring 'coffee and cake' in the afternoons. Baklava is lovely, of course, but stuffed full of sugar.
For beer try Efes and be wary of the Raki....
HTH and have a fabulous time. I'm really quite green with envy!