Mrs Ononeorange's bike is up for a complete winter overhaul, which includes replacing the very-tired-indeed rear mech (impressively pointy jockey wheels). I am a confirmed SRAM man and won't have any Shimano gear components on my bikes, so to me this is the work of the devil and I probably need to sacrifice some virgins or something before touching anything.
I know certain SRAM shifters don't work with certain SRAM mechs, but I have a feeling Shimano is a bewildering minefield of incompatibility. Her current rear mech is just marked "Deore", it would be nice to go up to XT. Can we? What do I need to look for? No idea what the shifters are (probably not very helpful...).

