Questions regarding gear shift knob... on Volvo s60 T5 2002

Hello, I am new to this forum. I have a Volvo S60 T5 2002. A few days ago, the gear shift knob button pretty much disintegrated in my hand. One of the plastic parts that was directly on top of the spring was totally loose. So, I was not able to shift gears with ease. The situation got worst, to the point I could not shift gears anymore.

So, i went online and learned how to change the gear shift knob button. I pulled out the knob, bought a new button. The problem is that some tiny pieces were stuck in the knob. As part of the process of changing the button, i completely took out the plastic mechanism that is inside the knob. The problem is, there was a long black plastic like bar (with a metal part at the bottom), that seemed to be attached to the plastic mechanism inside the knob, and now it is loose. That plastic long bar at the top has a little square in the middle. I assume that the metal bar inside the plastic mechanism that is in the rounded part of the knob should go in that hole. Anyway, I put the plastic mechanism and button into the knob, but the long plastic long bar seems to be loose. I tried several times to attach it to the knob mechanism but it becomes loose.

I put the knob back on my Volvo and the gears shifted twice but then got stuck again. I think it is because that long plastic black bar became detached from the knob.

so, the issue is....
1) is the gear shift knob damaged because the long black part is not securely attached? Can it be reattached? I can't even find a diagram that shows how the two are connect.
2) Should i just tow the car to the mechanic tomorrow to have it fixed? Can the car even be towed if the gears cannot be shifted?
3) Could i even drive the car without the gear shift knob. (I am assuming I can't)
3) Should I just buy a complete gear shift knob ($100) and attach it myself?


Thanks