Yeah, sounds like a project that commercial robotics companies, like iRobot, have
spent millions of $$ and multiple manyears developing.
Building a robot that can do something as seemingly mundane as climbing stairs has been
a major challenge right there. Also, coming up with nice control interface GUIs is another
major task.
I'll recommend one thing, the following guys make a whole series of gas detectors.
The best advice is get some off the shelf robotics platform and start there to learn the
ropes. The most important thing is ... your first robot is not gonna be your last robot
[if you don't fizzle out on the 1st one], and most people build many of them, bootstrapping
learning curve off of each one to design the next one.