Well, I truly hope you really are "determined to do what it takes and win his trust and let him know that he is home and will be loved" because you will have to have lots of patience and love for this poor confused guy. What is your grey's name? When you say he lost his mate, I am assuming that they were not really breeders just a young male and female who lived together, not nesting. More informationa about this will help.
First, relax and let your grey get use to his new home. He is, or course, frightened and unsure of that is happening so talk to him quietly and let he know what you are doing around him. Don't try and touch him, if he is unwilling to be touched. Let him come to you when he is ready.
Frankly, I am really excited for you and your new friend and believe with love and patience you will have a true companion for many years. There are oodles of threads about greys at the forum and if you have any questions, just ask. Welcome to the Grey family.