Used Z1 - want to buy

Hello gents!

I want to buy a used Z1 (WM558EA#ACB)

27'' LED IPS(2560x1440) E3-1225v2(3.2 GHz) 8GB (2x4GB)/256GB SSD/HD P4000/DVDRW/Cam/CardR/LAN/WiFi/BT/kbd/mse/W8Pro74 dwngr W7Pro64 (WM558EA#ACB)

Can you plz help me to tell that to lock for and give some advises.  And may be later install a new videocard. 

I need it for a lightroom foto (home use). And a big screen (now i have only notebooks at home.

And is here a reason to buy it now? 

Thanks