What Ghostrider has already said is good advice.
I also started with a Couch to 5k Program and made very fast progress so I am sure you will too!, I started outside and really struggled to get in to it on my first couple of runs, I was struggling so much.
Then I realised that I was going way too fast, the days of school cross country fresh in my mind
. I had a bit of an ache here and there, as is expected when starting something new or after a long absense but I kept to it and now, im under 30 mins on 5k and going for under 60 mins for the 10k!
Running is great John and I wish you the best of luck, the best part is that you are doing it!, I had friends who laughed at me when I started because of my laziness, which I admit is true, I still am a lazy git, but I am a lazy git who wakes up every other morning and does more that any other non runner I know!
As for a treadmill, I have been told that to simulate the outdoors it is wise to set it at a 3% incline. My advice is to go at a comfortable pace, where you could hold a conversation, but only with 2 or 3 word bursts, confusing but I hope you get what I mean 
My BIGGEST piece of advice though, is to follow the programs advice regarding warm up and cool downs, and then stretch well after the run. There is nothing worse than finding that you love something and then being told by your body to take a break, However if you do need to take a day off then don't be ashamed, I missed a few days of my C25K but I managed to get there in the end.
Best of luck John and please keep us posted!