As always.."it depends"....you need to read the release notes for 126.96.36.199 to make sure you dont have any custom code that may adversely be impacted. If not, then its a failry simple process. I also think your achitecture matter...single node versus cluster. Read the guide and if you have a single node environment with low risk to any existing code (based on release notes and guides)..then its a a fairly straightforward running of opatch scripts which should not take long. Of course, dont forget to regression test.