reusing instruments

MS 4. I copied a quartet with trumpet, alto sax, trombone and tuba and rejiggered it to be a trombone quartet. The instruments and parts I wound up with were a mess. I used the Instruments panel to replace and rename instruments. They seem to have names stored everywhere. The staves were named one thing, the parts were named something else, and they were all different from what I entered in the Instruments panel.

The MS3 Parts function was a mess, but the new one is even worse, if possible. I only need one name for instruments. If you copy an existing work and change the instruments, and then try to print or save out parts, it's a mess. Please simplify.