Nothing much really..provided it was well taken care off. being 90k I would change the timing belt. and depending on condition maybe valve cover leak, no big deal really.

Do check thoroughly because 90k for 11 years is like less than 10k km per year.

perodua engine in my experience is quite robust..had few of em and all are able to stand abuse lol. As for the car you're looking at, unless you open the engine you dont really know what has been change. justmake sure there is no excessive rattling/noise from the engine, aircond is cold and working correctly and no unusual noise from the suspension area. Check if there's any oil leakage around the block/on the floor. But do note that it is an old model, so don't expect everything to be perfect.

i'll call this typical problem for Kenari, as far as i encounter:
engine mounting
-genuine mounting will do the job, but expensive
front absorber mounting
-perodua alza is a good replacement
rusty and follow by broken exhaust rear section
-replacement will do
fuel gauge and/or temperature gauge malfunction
-halfcut replacement will do
radiator/aircond fan stop working
-because of aging, need to pay attention to this because there is only one fan, when aircond blow out wind without any coolness and/or temperature shoot up (that's why you need a working temp gauge), you need to do something
aircond not cold
-no solution

for buying second hand car, check for any bad accident repair mark and does the engine overheated. the rest is give and take, if you got other stuff in good condition, it's bonus; if it's not, accept it because it's second hand.

personally I wouldn't send to service centre, as I prefer going to our club (as in kenari club) recommended workshop. but yeah they will entertain you, even if you brought in kancil. But don't expect the price to be same as outside workshop.

but jaesern and kllam just diy their own cars

I usually go to bengkel yusof, puchong (after giatmara puchong besides ldp), or zastras autopart in selayang. there are a few more but cant recall right now.