It is likely that you will be dissatisfied with the sound quality of the FM link to the head unit. I have read way too many complaints about the FM transmitters and I avoided this completely. There are line level outputs for this unit but if you have a factory radio, you do not have the appropriate inputs.
I didn't see a price on the link you provided, but I wouldn't buy it for the above reasons.
I am currently working on getting my iPod to work with my factory head unit. I have a PAC iPAC-OEM that I am using. It is intended for connection through the CD Changer harness. My car doesn't have this wiring so I am adding it (sort of). When it is completed, I will be able to control the iPod through the head unit and steering wheel controls.
2001 Bonneville SE - Dark Bronzemist Metallic - Mods: 180* thermostat, iPod adapter, Digital OnStar Upgrade
Planned Audio System upgrades: Front & Rear 7 Band Equalizer, Amps, Hands Free Bluetooth Cell Phone kit
Planned mods: Front PEM, Ported LIM, Ported Heads, ZZP SR Rockers, Aluminum Gaskets & Reprogram PCM