Hi Elem510:
It is very common to have swelling in dependent areas after a neck dissection. In fact, it is common to instruct clients that this may occur during the immediate post-op phase and last for a variable amount of time depending on the person. My partner, Dave, had his radical neck dissection on almsot 2 months ago. He was very fortunate that his swelling resolved within a few weeks.
There are some neck exercises that can help as well as receiving therapeutic massage from a health care professional who also is licensed to perform massage therapy.
We also asked if being without lymph nodes can inhibit fighting off respiratory infection in the future and were told it can slightly but the nodes on the other side (if you still have them) compensate.
Nice to talk with you,
Kim