Any advice for DIY? I'm big on that thanks most of the rugs I'm looking at are hand knotted wool rugs probably with a cotton backing. I'm envisioning just cutting (very carefully and cleanly) the surged end off and joining the rugs. I can even hand sew the ends together (I'm capable) I'd have to repair the edge of the surge.

150 in northeast part of country

Having worked for a carpet installer when I was young, I would say hire a pro for not only cosmetic reasons, but safety as well. You want the runner tight! Not going to break the bank to have it professionally done, imho. Seek out a reputable rugger who has experience with stairs, check references and even go as far as seeing their work, if possible. A runner installed right will last the life of the runner, done wrong, there can be many nightmares, the biggest being safety.

I plan on converting carpet to wood on a home I've recently purchased. Floor planks are picked out -- 3 1/4" solid maple. My supplier can install them before I move in. My supplier does not do stairs, and even if they did, I don't know if I can make all the design choices before moving in, given limited access to the property. Should I delay the floors until I have the stairs figured out -- even if it means I'll then have to move around furniture? If not, should I have the floor supplier remove the rails and put in new edge and stair nosing -- so that the nosing has the same finish as the floors, and also so that the floors will be flush against the nosing? Or should I leave existing nosing/balusters/posts in place -- so that I have the flexibility to refinish them in place if it makes sense -- railings are in good shape, but I do not yet know what is underneath the stair carpet -- and if I'll have to put in new treads or will be able to finish the underlying wood.