One bit of advice: I got one of those inexpensive "assist" harnesses for my Aussie who was getting wobbly in his old age, but still insisted on sleeping upstairs with us. The harness was just a "girth" band with handles - worked fine going up the stairs; but going down, it could slip back around his hips if he fell forward. Which still gives you control, but they sort of don't like that....
I always meant to sew a strap that would have gone across his chest, so the harness couldn't slip backwards. But 90% of the time, he could bunny-hop down the steps on his own - the harness was just there so I could catch him if necessary. And he LIKED it (must have given him a sense of security?) - would not use the stairs until I put his harness on.