Hi Cowboy's Mom...I was going to mention hip problems earlier, but I tend to be one of those who toss in scary things and think that people might not want that info...but now that you have mentioned it...I must admit that you have a potential problem on your hands with the stairs...
When I had my dogs PennHip exams (to be sure that they did not have hip problems) the vet told me that there are several things you can do to help dogs avoid or at least reduce the chance of hip problems...
1) don't let them grow too quickly (watch their diet)...obviously, your baby has already reached his growth and he is really a huge dog...so I am afraid that if he already has hip problems, you are going to have to really watch and make sure that he does't get over weight.
2) don't let them play too roughly...no frisbee toss, no puppies crashing into each other and rolling about...(I know, easier said than done)
3) Watch out for stairs
4) No jogging until the puppy is at least 18 months of age
Now, given the fact that Cowboy is already very, very large and that he already has hip problems...the only thing you can work on is his activity. I suggest that you make a special visit to a vet (check the web for PennHip and they have a listing of vets that specialize in the test...which usually means that they also have a good understanding about hip problems) and see what you can do to minimize the growing possibility of Cowboy's bad hips.
I don't pretend to know what to do...and I certainly can't advise you about your personal situation...but I can, with near certainty, say that if Cowboy already has mild hip dysplasia (sp?) you are going to do some things differently.
However, if you still need for him to learn the stairs, the very best treat for us (my dogs will do anything for this) is tiny pieces of hot dog (you can get the turkey kind if you want). You could take a tiny piece and put it on the bottom step, praise when Cowboy gets it...then the next step, the next until he actually has to move up a step or two above his reach...then stop...and keep doing that same thing every day...after a while, either teach him to go down the steps from there or go up further...each week adding a few steps.
I hope that this helps...I hope that Cowboy keeps healthy and strong!