[JoeRedskin]

Definitely send the certified letter. In it, set out what you have asked them to do and when you asked them to do it. If possible, attach copies of your previous requests. Tell them what you are seeking now and ask for a response for a date certain. Don't threaten any legal action if they fail to comply just something along the lines of "we will explore our options on how to proceed". If they don't provide an answer (don't expect one), wait until they give you a final refusal to return the deposit (which they will, don't kid yourself into thinking this will resolve itself), then file for the mediation.

Understand, they have no legal obligation to do anything unless it is spelled out in the lease or by statute. If the lease does not require them to let you mitigate or provide the name of the contractor, etc., they don't have to do so. What you need to be doing is play for the end goal of having a court or mediator find them unreasonable in their claim for damages. Keep good records of all communications. Always emphasize you are simply seeking compliance with the lease terms and State laws.

They are playing hardball and being assholes. Use that to your advantage by making simple and reasonable requests. Quote the lease where possible. Don't let the stress show and get your mind set for a drawn out affair. (Not saying it will be, but it has the potential so prepare yourself for that contingency).