Soggy,
Right-clicking (or accessing the Contextual Menu as we used to say) with the Trackpad was a feature which became available in 10.4.7. You need to open System Preferences and click on "Trackpad". Enable "Two finger clicking", and it should work.
There is no other disk maintenance for you to do. As there are no known viruses at the moment (and I've not had one for almost two decades), there is relatively little to worry about. Disk defragmentation is done on the fly, although after a period of time, you might want to run something like DiskWarrior to optimise the drive. However, as with most things Mac, if it's not broken, don't try to fix it.
AppleMacster