I have not worked on Matsuura, but a Milling spindle does not vary much from machine to machine. Following are my points:
1. Why does the Clamping System Need Overhaul?
2. Please get detailed spindle drawing, incl. of clamping system from the MTB (the machine tool builder).
3. Normally, cleaning the collet of the clamping system is enough. This cleaning can be done by spraying solvants like diesel or WD40.
You may spray some low viscocity oil (hydraulic Oil) on the collet after cleaning.
4. The Clamping system of HSK tapers need more overhauling than BT or ISO spindles.
5. In case you have to dismantle the clamping system, be extremely careful, as the extremely high spring tension can cause personal injury. Therefore, please ask for correct procedure from the MTB.