For any DIY camera/lens repairs it's always worth having a look here: and using the search facility.
Another website that is very helpful for all things Pentax (including Takumar lenses) is:
Once you've done one or two and got a general feel for the way these things are typically put together, then small variations are easy to second guess. I've never found a Pentax lens where the fungus has left any permanent damage, but perhaps that's only because of the particular types, ages or SMC of the lenses I have. Do clean around inside the lens to try to catch any spores lurking elsewhere in the workings, especially around the edges of the retaining rings. I use carbon tetrachloride, which I was told many years ago kills fungus on slides and lenses. Apparently it is also carcinogenic, so may not do much for the health of photographers either if used to excess!

Best wishes,