Yes you can switch, if it will work is another matter.

1st issue, is you are using a 9 speed rear dérailleur with a 10 speed setup, as that's shimano, that means is should have a Dyna-Sys RD as you are using MTB parts, so you really need a Dyna-Sys rear mech. Ideally what you want is something like a M675 SGS rear dérailleur for this type of setup.

Using a GS RD on anything over a 32T cassette can be temperamental even though it is spec'd to work up to a 34T, and will have some give to go to a 36T.

What type of bike are you running this on, as it sounds more like a CX setup than a MTB which a 11-36T would be associated with. You haven't mentioned the shifters you are using, which could complicate everything depending what you are using, as Dyna-Sys RD's only work with Dyna-Sys shifters.