Flash Player fails to Install

Dear Forum,

Here is my situation

- I have an iMAC G5 ( 6 years old) OS X 10.5.8

- About two weeks ago, I was on Facebook and could not open any of the youtube or otehr videos posted by members

- Message said " Flash Player upgrade required"  

- So, I went to Flash download website but find out that for my system (Power PC 10.5.8) I have to go to the old archived download module

   but there are a whole bunch  10.1, 10.9, 10.1.64, 10.1.xxx and so on.

- I tried downloading 10.1 Flash Player on my MAC but it bombs out every time during install....ie. around 50% compeltion it just says "Install Failed"

- To make matters worse, in the midst of this confusion, I accidentally 'uninstalled' the flash player that I originally had, so now, I cannot see any You Tube videos !!!!

- My only hope is to drag my computer to an Apple store and get their help.

- I do not have any kind of a Firewall, I have enabled 'Plug-ins' in my Safari Browser, .....the only security i have is my Wi-Fi is Password protected.

Any ideas please....I am going around in endless loops.

Thanks