When you compost you need to include as much 'green' matter as you do 'brown' matter, i.e. those dreaded grass clippings to straw. You are correct, if you don't add nitrogenous materials, the nitrogen that is present will be consumed during the composting process.
If you're looking for a good soil amendment to add nitrogen (and a considerable amount of trace minerals and other goodies) go with Kelp Meal. I get mine through the mail fairly inexpensively by the 50 pound sack, and the soil microbes go crazy over it! Urea is pretty harsh and will kill a lot of soil life if used improperly, but I trust you're the kind of person to do your research on dosage before just chucking it in your soil.
The PH can be sorted out over time with lime, I use dolomitic, but better to do it slowly rather than all at once. Also, best to till it in a bit before you plant in it, to let it settle the soil and not be so 'hot'. Fall is best, but spring is ok in March/April if planting in May/June.
If the straw is screwing your soil, call the local tree services and ask for some free hardwood chips. I like to specify that I only want chips from clean trees, as one time I got a load with poison ivy vines growing up the tree... NOT a good situation to say the least... But the hardwood chips will last all season, are usually free, will attract a multitude of worms which will add all natural fertilizer, and allow you to have the biggest damn azurescens patch in the neighborhood!

Usually need to give them a spot to dump it, but for free, no matter to me?
Sorry Fruitbat for getting off topic.