We decided to have our soil professionally tested. After some research we found that it can be easily done through University of Massachusetts Amherst. (Here is the website http://www.umass.edu/soiltest/). We took samples of the beds and the earth they were on top of and sent them off to to be tested.
Thankfully the tests came back with a safe results for the raised beds. (We had used only our compost and topsoil purchased for gardening at the local gardening supply store). The earth outside of the beds however tested with very high levels of lead, an unsafe (for growing food you want to eat, as well as do not inhale dust) amount of lead.
Here is a document on how to interpret your test results.
We ordered landscaping fabric from FarmTek (www.farmtek.com) to put a liner in between the beds and garden soil. Knowing that we'll loose some soil in the process of moving everything out and back, we also purchased 10 additional bags of cheap, but clean, top soil. For the fertilizer, we opted to go the natural way: 6 bags of composted manure and a small bag of bone meal.
We set out a tarp to transfer the soil from the beds to. (If you use this method be sure to use an old tarp that you will not mind putting a few holes in with all the shoveling. It’s hard to avoid, especially if you have enlisted the help of an enthusiastic seven year old.) We removed the topsoil from the bed leaving an inch or two of it behind as a buffer and then put the landscaping fabric down in the beds pinning it in the corners with ground staples. If you are mixing in compost with your topsoil I would recommend doing so in a wheel barrel or on a tarp before adding it to the beds if you are concerned about disturbing the liner you put in place.
This whole process took us the greater part of the day but was well worth it for the piece of mind. We already replanted winter garlic and asparagus that were in there before, and after only two days in the new soil they are looking better then before. All this moving and shaking did not hurt them a bit, it helped loosen the soil and in the process got rid of some nasty grubs. (Our backyard helpers: robins were very happy with the meal provided in the process!) We also seeded the first crop of the season: spinach, arugula, lettuces, beets, kale, dill and mustard greens. All those are hardy plants that actually like cooler weather, and we should have some fresh greens to put on the table soon!