lets put it this way.if u like your suspension now (the feeling, the ride and height) i think its best for you to re-service.
i have seen the service parts for TEIN in the warehouse and those are the goodies.
Re-service : 400X4=1600 (hidden charges may apply MORE if they are badly damage)
brand new: 3500-4500, and brand new only sells the new versions, 1 year warranty
buying 2nd hand again: 1500-2500 (the risk is still there, win-lose situation)
but if u dont like tein and u like cusco, zeal or whatever japanese brand..then u have to bare the risk and repair it at any normal shops.
if u decide to go for local, i would suggest titan since they have good reservice center. affordable and hassle free.
just my 2 cents opinion