http://bgpictures.com/2011/03/11/hp-z3100-drive-belt-replacement-how-to-video/
The video is excellent. I used that plus the official manual do the belt on my z3100. I put the small parts for each group as noted in the video into plastic bags and the larger parts into a box. That way everything was organized when I started re-assembly.
In addition to the tools recommended, use some lighter fluid and lint free towels to clean the rails upon which the carriage assembly glides. Of course use a fan to dissipate the fumes. Lighter fluid is one of the best cleaning media around for metal. It does a fabulous job and leaves no residue. You’ll be amazed at what comes off what appears to be clean steel. Don’t use it on plastic.
When the printer is apart make sure that all electrical connectors are firmly seated.
Plan on about 4 hours or so for disassembly and cleaning, and about that much time for re-assembly. I suggest using latex gloves to keep finger prints and oils off of the parts.
