On the siege thing: Probably. An ill prepared city or castle can fall very quickly - but a well prepared one lasts for a while.
Out of curiosity, what exactly were you planning? In terms of the results, I mean.
From the books and sources i use about Manuel, i can see him assaulting the settlement, despite the inevitably heavy cost in terms of his men because of the trouble the Seljuks have been and how Manuel was in OTL, excitable and energetic, so an assault it is.
If you mean about the whole campaign? Well, he is going to have to rest for a while and go back to the capital and celebrate. I can't really see him taking back Anatolia in this season. He is going to prepare, plan and eventually take it back, hopefully.