Before anything, I must explain that I'm not a expert; however, I update my GPSs many times and I thing I know how to do.
To chose files, look for a number near and above. Example: to replace D3543020A.sid you look for D3543030A.sid Sometimes this files can be the same.

To the second question, I don't know your device; but the answer is your device may be not able to use all functionality of this maps and you don't need all those files, something common.

Best regards, hope been helpful!