do u even have the tools to DIY?
if u ask me, take it to the workshop and let them do it, u just buy the ATF

the position of the GB oil sump is not as convenient as other auto car
the position is at the left side ...near the tyre there
but its quite deep inside and something is there blocking the way
thats why i prefer u to do it outside at workshop, their jack is better, make it slighly easier to reach, normal jack is abit hard
and its gonna be messy, i've seen mechanic did to mine, since something is blocking the way, it causes it to spill everywhere

proton original ATF which is same as the mitsubishi diaqueen spIII
or u can use toyota T-IV
or u can use aisin ATF