OP, you're jumping the gun here.
What you need to do.
1. Send the landlord your new address in writing as requested.
2. Wait until you get the information regarding the status of your security deposit.
3. If you disagree with the amount kept, write your demand letter. Give the landlord a certain amount of time (say, two weeks after they receive the letter) to return what you believe you are fairly owed.
4. If no response (or one that is not to your satisfaction), THEN you consider a lawsuit over these funds. Such lawsuits are typically handled through Small Claims as they involve relatively small amounts of money in dispute.
5. The court will decide who is "more right".
Gail