Installing lion osx from snow leopard with time machine

Hi there

My dad has a 2011 iMac with snow leopard on it. He also has time machine running.

I want to get him unto lion

When installing From app store does it go over the top off snow leopard iris it a complete reinstall?

If it is ontop of do I need to tell it to read from time machine

And finally - for now ;D -how long does the lion install take on average (using fiberoptic bb)

Thanks

The Lion install from the App Store should install over top of his existing Snow Leopard installation. Data loss should not occur as long as all his data is stored in the proper places. As with any OS install (or anything that makes drastic changes to your hard drive) you should have a current backup in case things go wrong.

Worst case, if things get completely messed up (which they shouldn't) you do a clean install (make a DVD or USB flash drive installer before you launch the "Install OS X Lion" app you download...instructions can be found online) and tell it to restore from your Time Machine backup.

Yes, make sure Time Machine has been run at least once before downloading and installing Lion. Everything should go very smoothly, since it installs "in place," but just in case ...

Thanks guys - really appreciated