rock-star_79, I am not sure about swapping out the UI30.res file so do that at your own risk. There is no way to extract a full firmware as some of the files are not present on the player, these are used to allocate firmware space, scan the player hardware and prepare the memory to load the firmware but are not actually put on the player.
When modding your firmware always use a copy of your firmware never the original that way if you do stuff it which is rare you always have the original.
Images can only be extracted one at a time using the export button in s1res. However you can just dragand drop images for loading them to the firmware.
The ability to browse for files did not become available until the release of 3.5.37 but is not included in all firmware. It is possible to add file browsing to the firmware and "lattesurf" has done an excellent guide on doing this here:
http://www.mympxplayer.org/how-to-en...er-vt2730.html