Hi,
I'd begin by getting the car in good condition first, basically giving it a overall service, those should be your first modifications
as it's best to have the car in good condition to start off if you plan doing any performance modifications, or any performance driving.
Check the whole car inside/out. Oil, Oil Filter, Spark plugs and leads if needed. Do a coolant change
and it's a really good idea to replace the radiator if blocked/damaged, takes experience to know what needs changing so it's a good idea
to have a mate help you out.
It's a VERY good idea to replace the fuel filter too. Clean throttle body and Idle Speed Control Valve
Get the car up on all 4 wheels, or 2 at a time and check each wheel for freeplay and fix cause if excessive,
worn bushes/ball joints and bearings constantly affect wheel alignment as you drive. Check the brakes and
brake lines, check the handbrake and adjust if needed
If Auto give the transmission a fluid+filter change. Check all 4 wheels when up in the air
for any play and rectify the problems.
Check the belt and pulleys, they do get worn over time.
King Lows are ok, but if you want to get extra low, consider getting a strut/spring combo, or even coil overs if you like as it's important to have
a good spring/shock combo, it's ok if your only lowering a bit.
Service Manuals - Gregories is your best bet 2nd to the GMH one which are hard to get a hold of. Stay away from Max Elleries as their "wiring diagrams" are rubbish,
but they seem to have more pages. I'd just stick with the Gregories and read it as they are helpful.
When you get the car in a good condition and you want to begin doing performance mods here are some suggestions.
Higher ratio roller rockers from FIT Performance... check out their website
Cold Air Intake will help out a bit
Heat insulator spacer for inlet manifold... apparently gives a bit more power.
Then you can get a Tuned memcal from Greenfoam or Delcowizz who are on this forum
Extractors and Exhaust.... it's a good idea to do lots of reading on the subjects of extractors and exhausts before chosing, see what people run and whats best, the V6's
can have a horrible sound if you don't get the correct setup which I'm sure we've all heard. If there are good off the shelf exhausts for your car, you could buy one
and install it yourself.