It's definately best to plan CTA if you can, no harm in asking.
I was once coming in from the east and I got a clearance, just after I got inside the CTA the duty rwy at tulla was switched to 34. This created quite of a headache for the controller but he was nice enough to vector me around a little bit and get me to Essendon without having to spit me out
. The tower guys at EN are also very good and will help you get in.