When we first moved into this house, everything was brass.  I mean EVERYTHING.  Lighting fixtures, door hardware, medicine cabinets, switchplate covers.. If it could be brass, it was!

One of the first things I did, was rip out the brass sliding glass doors which were on the girls' bathtub.  Not only were they ugly golden brass, but it was a GIANT pain in the butt to bathe your kids in a tub with doors. 

First you need to remove the doors from the track, and then remove the three screws on each side of the track that hold it to the tub surround (or wall.)

The track may still be stuck down with caulk or liquid nails, so just keep prying it up until it pops off. 
Once your tracks are off, it will reveal another reason that sliding glass doors are NASTY:

That is all the crap that collected under the track.  Disgusting moldy crud.  Fortunately it only takes a little elbow grease and a razor blade to get rid of it.  (I did have to bleach some of the caulk to get the discoloration off.)

Once the doors were off, the brass fixtures were screaming to be replaced.  What should have been a straightforward project turned into a little bit of a nightmare because the valve which supports the shower handle would only accept Price Pfister faucets manufactured before 1994 (it was from the "09 series" in case you have one too!)

Therefore used an universal retro trim kit for the internal handle mounting hardware and splash guard along with the actual Price Pfister Pasadena handle, spout, and shower-head.
 (Since doing this project I have since learned that you can buy Pfister Retrofit Kits at the plumbing supply store or even Amazon which would make the retro trim kit unnecessary.  See how far I've come!?!)