could somebody direct me to a DIY on how to install HID low-beams for series I?
i couldn't find any

i have been thinking about buying these:

04-09 Mazda RX8 H7 6000K HID Kit for Low Beam Headlights :: RX8 :: Mazda :: Lighting - HID Conversion Kit :: Dash Z Racing

in general, how long do hid's last?

 

Do you have a base model or Sport Base without factory HIDS? IF so it's easy, go with the ddmtuning HID's and follow the instructions that come with the kit. The HID's you linked are in a youtube comparison video I watched a while back and IIRC they were shitty.

 

I need a pair of HID myself, the driver side went out a couple of days ago. Now, its one eye blind...lol

 

Good HIDs should last a while. For the love of God, don't install HID bulbs into halogen reflector housings; you'll blind everybody on the road and generally be an asshat.

 

As long as he doesn't install them into the brights then he should be fine. Unless something is different with the headlights between the s1 and s2 he should have a halogen projector which is not ideal but it does have a cut off for the light at least.