After market warning lights.

Quick question to those with electrical knowledge (not me).  I am very
handy with mechanical work with cars, but when it comes to electrical i
know nothing.  I am looking to install a pair of aftermarket "wig-wag"
flasher, or a pair of rear hide-away halogon flasher system.  I am
shooting to install them in the rear amber blinker housing, for
roadside warning when on construction jobs.  My first question to you
are, which system would work better for my situation.  A wig-wag
flasher system not for use for headlights but for my "blinkers" if
possable.  or use a system similar to this product:
http://www.galls.com/style.html?assort=general_catalog&style=GR136&cat27%07

Id perfer the wig wag product only cause its cheaper, but what ever
advice you can provide would be great! please and thank you.

Also one more question, when i look at the wiring diagrams of some
products.  it says connect the flasher system to the battery, but how
am i supposed to go about doing that?! i look under the hood of my 99
chevy malibu and only see 1 large red wire coming from the battery.
How do i connect it?! also wiring a fuse, what the deal with that?

Any answers to any of my questions will be of the upmost help to me.
also if you have any questions for me regarding cars, dont hesitate to
ask.
Thanks,
John p.