SF since u said never change ATF,change it 1st,if u drive in town most of the time,is better u change every 10 - 15k interval,since no more warranty,u wan cheaper can go to any under cherry tree mech can do it,nth much complicated wif the engine...anyway,real prob...only u and the mech will knw,as u send for him to check,we all here juz can giv opinion...
spark plugs,doesnt necessary for u to change to aftermarket,just use back the OEM 1 is more than enuf as ur car oso nt that for performance and nth much u can feel(well at least from me changing spark plug i din really feel the diff,mayb my senses had numb)
ur version punya altis kah....GB prob i dunno,i juz knw driveshaft,den the rubber lining prob nia,as tat is wat my dad customer complain lar...