I've built one of these. Good fun, but of course battery life does not match the 7+ years of the original. I think mine lasted close to a year?
If I remember correctly the magnetometer was end of life, but not critial to it's operation.
I'm not the original author, but I am considering ordering a few new boards and maybe the components. If you're really interested, give a shout on github: https://github.com/carrotIndustries/pluto/issues/1