Raw beginner questions

So far, it is My limit that we are enduring, but I will toughen up and smarten up. I have 2 Morgans, not exactly the ideal endurance horses as you will see. Billie, my 4-legged teacher, is 20 years old and he and I go at the same speed. We are good for each other. He has taught me everything I know about horses in the four years that he has been in my yard. Well, today I tried to get his resting heart rate... "right behind the left elbow", well, all I heard was this real deep thud every 5 seconds. It didn't sound like a lub-dub. I think it was his breathing. And he was grazing at the time. I suppose out on the trail that their hearts are beating much louder so they are easier to hear. Is this the case? My question for today is, what is the best way to get a resting heart rate on a horse?

My other horse is a 2-year old Morgan colt. He is a real sweetie and I guess he will need to be fixed soon, so he stays a sweetie. He and I might be ready for each other at the same time, somewhere around the turn of the century. Next question, I hear mention of several stallions on ridecamp. Is there any reason to keep a colt a stallion except for breeding purposes? Some people even say that a gelding has less health problems and lives longer. Anyone have experience in these matters. I dont. These are the first two horses I have owned.