springs dont normally wear out... struts do.

i would leave your springs and get a set of the KYB GR2 struts. i have the GR2's on my Z34 i also have the eibach springs.

for suspension upgrades:
-sway bar bushings. OEM if you get the energy suspension bushings DO NOT USE the brackets that come with them... they will break! they are weak steel and crack. if you must use your stock brackets and a piece of the old bushing to fill up the gaps.

-Strut Tower braces. make a world of diff!
-wider tires atleast upfront. go to 245's by what ever fits. 16' 17' ect.


other things i would do are as follows:
-fuel filter
-flush the brake fluid wiht all new fluid
-check your engine mounts for cracks and replace if ness.
-trany fluid/filter change
-professional injector cleaning. they hook the car up to a machine that presure cleans them.
-plugs and wires
- check battery grounds and any Neg grounded to the body for corrosion and clean.
-deff coolent flush
-check the CV boost for tears on the axle
-look for any leaks

these are all the things i would do if i just got a new Used car.