FlyNavy,
Lots of good info/advice in previous posts. I was in similar situation to you and decided to give it a go as I missed flying and more importantly being around flying people. Last flew in 2009, retired in 2013 (did some drone testing that does not count toward 121) and had a good defense contracting job. Took the ATP written before deadline, then did 10 hours of Duchess time but wanted to do something more substantial training wise. Did ATP (Former HPA) 737NG Type and ATP in Spring of 2015 (removed CL thrust restriction). Very good program but not cheap and was able to use GI Bill to cover most of cost.
Listened to advice from friends and did 6 months with regional and then was picked up by ULCC where I live. Each had decent training and now feel comfortable in 121 environment. Low pay and some commuting but experience worth it. Just received CJO from legacy exactly a year after getting ATP.
While there are some outliers, most majors still want to see some 121 time and even though mins are being lowered at some airlines, 100 hours of recent flying still seems to be gatekeeper in computer algorithms to get app through system.
While at times I have wondered why no calls like everyone else, when I look back, the last year has gone by very fast and glad I had the time to prepare for each step. Things will happen fast for you, just stick to your plan.
PM me if I can help in anyway...lots of folks helped me and happy to pay it forward to others.