Most likely if they are going to install in a condo unit, they will be installing a fiber jack. These little white boxes are normally installed near the baseboard, and they look like this:
From here, they'll connect the fiber cable (yellow cable above) to the ONT (brought by the technician).
The black cable you see coming into the picture above was fiber coming from outside. Most likely since there is already fiber in your building, the fiber going into the jack will most likely be the indoor kind (the tiny yellow cable). These indoor fiber cables are quite small (think the size of a spaghetti noodle). So cable management should be simple enough.
But yes, to answer your original question, you will need an ONT in your unit.
As for ONT placement, all FiOS service (TV, Phone, and Internet) go through the ONT. If you were getting stand alone Internet you can pretty much put the ONT anywhere that you want. For the phone service, the signal has to come from the ONT, so it might be helpful to put it near an existing phone jack. However if you use a wireless phone system and don't plan on using the wired jacks, you can put the ONT anywhere you like, and plug the wireless phone system directly into it.
The ONTs themselves are pretty small, about the size of a router. Here is a photo of one of the indoor units, with the power supply next to it:
For the wire ducting, I would wait until your installation is finished to see how to route the cables. The yellow spaghetti fiber cables are quite delicate, any if they get pinched or bent in a wire duct it could break the cable. Just something to consider.
Also just a heads up, lots of the installations are completley up to the installer, and could be different from what I stated, but it should be pretty similar.
Best of luck, enjoy super fast Internet!