Daytime lights are halogen. Yes, replacing them, you should use lights with matching setups. You can always upgrade your halogens with aftermarket hid kits but it's not advisable considering the heat output unless you use 35 watt bulbs and not the 55 watt versions. Cart before the horse.
You have a LCM, light control module, that understands that you have halogen and xenon bulbs. If you buy a set of lights with different setups, it can cause error messages. I say can, all depending on the lights you buy.

If you'll be going other than OEM, I hear people like the ones from DEPO. I just bought a set of Spyder lights and am not expecting miracles but I'm hopeful.

I'll try to open up and clean the OEM's that will be replaced and keep them as spares or sell them on the 'ol eBay.

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'03 4.6is (the wife' s ride)