Difficult. You have to consider that its actually done the bike more harm than good sitting around all that time, and even if its has been 'serviced' theres still a fair few perishables (seals, bearings, tyres etc) that would need replacing. If I was buying this bike then id want it torn apart before I even thought of running it. But then again Id probably just stick it in the front room..
Let me know what you decide..picture and a story would be nice...
All the best
Nat