I've just spent £280 on having it serviced, and having a brand new shaft and hose fitted. This was done at KAIS suspension. The shock has not even been fitted since this work.
Not sure what weight the spring is but it is marked with 1092-64-160-330. It seemed too soft for me (I'm 19 stone).
With the work just done to it, it should function just as well as a new one. I believe these retail for £1000 on ebay.
I'm looking for £500