If you're on Kmeaw (w/e vers.) just do a backup (If not, use the in-built PS3's backup utility), but first you need to format your new HDD to Fat32 so that the PS3 can see it (because anything else wont show up at all) then you need to let the PS3 format it to its own file system.
Now for the methods
Plug it in any of the 2 USB ports via a SATA-to-USB Enclosure (or buy yourself a HDD dock such as this newegg.com/Product/Product.aspx?Item=N82E16817153066). What's cool about the HDD dock method is that you can pretty much use your new HDD in your PS3 and use your old one in your HDD dock without even moving anything. just switch them out and voila... brand new HDD in PS3.. and old HDD outside for your movies, pictures, gamesaves, and etc etc
However, i don't think your games can be booted externally (unless Kmeaw can boot games from external drives hurrrr)
Anyhow, buy a HDD Dock... that Thermaltake dock costs like 34+ $ max (newegg has it at 28$) depending on the tax and shit
That 160GB HDD , is it the HDD you want to use in your PS3 (internal) ? and use the old 40GB as external?