Glad to hear that you have got your Mr sensible hat on
You are approaching this in the correct frame of mind and you will have a hoot with the Zee on track once you sort your brakes, tyres, suspension and you shed a bit weight.
I have been running circa 650 bhp on my track 350Z Roadster for 5 years now so I am in a position to be able to guide you through the do's and dont's for loadsa track fun.
Once you are sorted then basically all you will have to do is keep the car in fuel, tyres and brakes.
Regarding coil overs, there are many options as I have previously said, however much will depend on your budget and if you really can be bothered with 3 way adjustment as I know of many peeps who have bought expensive 3 way coil overs and never readjusted them after the initial settings, so this is the area which IMHO requires the most consideration. The rest is a no brainer.
Alex