kc, I never done yet maybe you can try this site using FPX let me know is it work?
http://www.mdks.gov.my/web/guest/e-bayar

every Monday have a moving office MDKS for payment cukai taksiran at pasar malam DC .

If DS intermediate, normal extension, just go to their office and buy the standard plans.
Call them first to find out what documents to bring. If lucky you may be able to get everything done in one trip. Cost RM1000++ including 500 deposit for disposal bin.

If non-standard very extensive renov, or corner or SemiD, then have to draw plans. There are many restrictions on how many feet from the fence and so on.
Simplest way is to pay your contractor to do it. They know who to go to. Cost RM2500+-
Check the final plans before they send it.

Be aware that with MDKS, renovation will increase your annual assessment rate a bit. Because you can now rent out the house for more, and the rates are based on estimated rental.
I read somewhere that if you have awnings, there is an extra charge of RM35 per year. Something like that.