I have a 5 Million dollar lawsuit filed in Federal Court.

The file always belongs to the client. You can demand your file at any time and your attorney must provide it to you. Refusing to return a client's file that only newbie lawyers make. Having said that, be very careful. Changing horses in midstream or lawyers in the middle of a lawsuit is very often a bad idea. You should consider this under only the most extreme circumstances. You have not specifically said why you want to change attorneys. You have only mentioned that the attorney has had "this" for over three years. To a layman, three years may seem like a very long time. In complex litigation (which this probably is it if involves the reports of multiple experts), three years is not long at all. My suggestion is that you have a candid discourse with your current attorney before you start looking for another one. Feel free to express your dissatisfaction, but do not become adversarial. If after this discussion, you feel that you are not being adequately represented, you may want to look for another lawyer. Realize that it is always difficult to get one attorney to take over a case started by another. I personally will not do it. It is even more difficult to get a second attorney to represent someone who couldn't get along with the first. That is just asking for trouble. You also have to realize that your present attorney is entitled to be paid for the time and expenses which he has put in on the case to date. If your present attorney is representing you on a contingent fee basis, there is the possibility that you could end up paying two contingent fees (i.e. 60 - 80% of any recovery - before expenses are taken out).

Original attorney is entitled to be paid for his disbursements on the file and to keep a retaining lien against the recovery on the case.

Why not just reimburse your soon-to-be former attorney for the money that attorney has already paid on your behalf for the reports?