Did they book the $ 4,000 into evidence as contraband as evidence of sales? If they did not then you should file a claim against the police agency as soon as possible because there are time limts, and if you are denied that is your right to sue letter. Consult with a criminal defense attorney regarding the criminal charges and inquire about how to handle the possible civil case you have, it will depend on the report.
It's unclear if the cops took the 4k as evidence of drug sales or simply stole the money. If it's evidence your attorney can file a motion to get it back though the DA may oppose this and argue this is evidence and you should only get
this back if the matter is dismissed. If the cops simply stole the money, you're likely out of luck as it'll be your word (someone facing a criminal case) vs. the cop(s) that arrested you. Obviously you need an attorney asap and you should discuss this with him as soon as possible. Best of luck.
Get a good lawyer and enter not guilty pleas to the charges. You can do a motion to return property to try to get the money returned at some point, or maybe the prosecutor will agree to such a return of the $4000. But you have not said what the evidence is against you, so it is impossible to say what your chances are of beating the charges.