I have a KX040-4 mini excavator and some of the lower truck rollers are beginning to leak. I looked at the parts schematic and it shows a plug which leads me to believe I can rebuild it. I have a couple questions/requests...1) Can these be rebuilt instead of replaced? and 2) if possible to rebuild, is it better to rebuild or buy a new roller assembly and replace the leaking one? Any guidance/insight/wisdom is appreciated.