Not necessary to pull an engine to remove the risers and manifolds. So, maybe look elsewhere for the work to be done. My guess is that they would charge for such, but not actually do it that way.
You stated 10-15,000 CDN as the cost estimate, thinking you meant $1,000-$1,500
The space in between the engines is tight, but once you get inside of one engine off, then the other is a cakewalk.