I"m thinking of chanigin the oil and cleaning the tanks and pump heads so what should I use to clean these things ? and Is there anything I should keep into consideration or it is pretty straight forward?
Its pretty staight forward. Just disassemble everything & put it back the way you took it apart. While its apart, you may wanna consider replacing all the seals instead of reusing the used ones.
We use an areosol degreaser made by GUNK, if you can't find that, get their engine degreaser. It'll work just fine as well.