You should be able to keep most of your stuff, but keep in mind that you should not backdate worlds. If you are playing on a Minecraft 1.7 server you can't use Tekkit because Tekkit uses Minecraft 1.6. It might work, but it probably wont and everything in 1.7 that isnt in 1.6 like podzol, stained glass, dark oak and acacia trees, as well as the new biomes will not be carried over. If for whatever reason you are playing on a 1.6 server it should be okay, but I'd start a new world anyway.
Also, this has nothing to do with Redstone in Motion, so you should have made a new thread.