Generally its pretty safe, indeed, safer than much of Western Europe...unless of course you get diverted to Kosovo or Georgia or something...then you may want to be more cautious.
Petty crime is rife - so just the usual common sense of keeping personal documents out of sight and money on an inside coat pocket or something.
You do need to watch out for "policemen" who aren't as they often target lone females and offer useful advice, only to con you.
Romania is the most wonderful country. I've only touched on it but I would hugely recomend it (going back there next September on a gap year tour) - Transylvania is not a cliche, its wonderful - I would avoid the cheesy "Dracular tours". Its a very civilised country...for the most part...Bran castle is worth a visit and shrouded in myth, it lives up to Transylvania's romantic image. Its a fairy tale castle and not a Dracular castle so you avoid the tourist hords who think that Romania = Dracular so avoid everything else. But thats all I've really done in Romania...
Phrase books - Lonely Planet do a good one for Europe covering all of the European languages (including Arabic).
As for sleeping bags - depends as to how much you're willing to rough it. Most hostels do not provide bedding and many of the cheaper hostels are not the most...erm...clean...so you may find yourself sharing a bed with a multitude of other erm...creepy crawleys. I personally wouldn't bother with a full sleeping bag, just a thin blanket or something just for extra insulation.
Istanbul - use common sense as it is Muslim country so avoid showing shoulders and wear long skirts/trousers. Visit the blue mosque, I think its called...not been there myself but I've heard its incredible.