Effect of wine used for deglazing on dish
Unless the recipe calls for a fortified or sweet wine (e.g. madeira, sherry) use a dry or very dry wine, usually white, but not always. You can easily ruin a dish using a sweeter wine, as I once did with risotto.

Whether or not the flavor of the wine comes through depends entirely on the wine used and the quantity. If the recipe calls for a cup of wine, then you will probably notice it in the final dish. If used just to deglaze a pan, then you probably won't notice it at all. 

Old wine is fine as long as it's palatable and/or hasn't soured. Beer works great as well.