very good and usefull information, thank you very very much!
I was planning it because I had 3 lose bolts. I just want to check that the gasket hasn't moved. A friend told me into this, just in case.. But since you think that it isn't necessary, I think I won't be bothered eather.
For installing the lower half, just a new gasket will do, or do I need to apply some sealant? (what kind, brand?)
I am getting to know the M42 a bit, I removed the head from my first, and swapped my second

I can use an engine jack (crane?) for the job.
Anyway, I felt very lucky when I didn't found any debris of the distribution.