I've got an Allez Sport 2014 edition which is fitted with a SORA 9 speed groupset. The rear cassette is an HG-50, 9-speed, 12-27T. I'm looking at purchasing an 11-30T version of the 9 speed HG-50 to get up some sharp hills which are, at times, ruining my fun on rides.
Firstly, could someone advise whether or not such a cassette would inherently be compatible with the rest of my groupset? I can't see why not as it's the same branding and same number of rings. My only thought was would the chain be okay with the extra 3 teeth?
Secondly, how easy would it be to change the cassette? Something which may be feasible for a relative newby to bike mechanics?
Thanks in advance.