I have read lot of lines about several system update .... but i can't find simply what i want.

I explain myself:
I have an activation code for both sles10sp3 and oe2sp3, and i would like to use "Yast online update" or "rug": same for me if one of this two works fine.

I would like to know first, if it's a good idea to apply all SLES and OES2patches (except sp4 which is incompatible as I read) ?
And if "yes", in which chronological order:
- Install SLES10
- Update SLES
- Install OES2sp3
- Update OES2

- Install SLES, install and configure OES2
- Update both

Thanks for all