"She says he'll be real easy to rehab"
If he has been neglected over the years then you may have a long road ahead of you im afraid ,it's not as easy as the owners quote above.Patience is the key word here,im sure you are fully aware of what your taking on but changes are going to take time.The grey will need time to adapt to his new owners & environment,he needs to gain your trust so you can build on a relationship with him.
The first thing i would suggest is a full exam with an avian vet to determine his health & if there is any medical reasons for the plucking,if he hasnt had time spent with him it may be due to bordom,lack of stimulation etc..if you do a search you will find many threads on plucking.
Do you know what kind of diet he is on ? Again a poor diet can lead to health problems.We have a bird food room which has various topics on diet,so worth popping in there & having a good read.
As for biting greys bite for a reason,it may be fear,aggresion,instinct,attention seeking etc.. You need to find out in what situations he is biting in,then we can work on resolving them.
Many of our members have taken on older greys so will be along with their advice,it may be a long road but given time & patience it is very rewarding taking on an older grey & as a forum we will endeavour to help you.