would a statue of limitations prevent me from releasing my lawyer I've had for 4 years to get a new lawyer?

First, the Statute of Limitations simply means you must file a law suit before the time period elapses (4 years for a typical negligence claim). The only relevance to hiring a new lawyer is the significant attorneys fees the former lawyer will seek out of the eventual recovery. Assuming he/she had the case for a few years they could be entitled to a significant percentage of the attorney fees generated in the case. That could make hiring a new lawyer very difficult. I don't know the circumstances of your claim, but if the lawyer is fired "for cause",  then he/she may not be entitled to claim a fee for the work they put into the case. Proving cause, is very difficult and the conduct would have to be egregious. (technically the former attorney's fee comes from the client's share of proceeds, but most lawyers agree to take it out of their percentage. That is something you need to raise with any lawyer you speak with. If you are unhappy with your lawyer, I strongly suggest you consult with another qualified lawyer in your area. Only from a detailed conversation can the other lawyer understand what the fact are and whether to assume a case that has been ongoing for so long.