I am a novice at all this plumbing stuff, but am fed up with the lack of quality service I have received so I am venturing into the assembly of my vessel sink.

First, the tile guys cut the granite counter wrong and I need to enlarge the holes. Seems that using an alpha core bit on a regular drill might do the trick. Need confirmation or another suggestion, please.

Second, how do I secure slip joint extension tube to the pipe that runs out of bottom of sink? And, the extension pipe going into the ptrap seems to just sit in there, is that right? Do I need to use plumbers putty or any other adhesive when joining the pipes?

Lastly, the house drain pipe coming out of the wall is pvc and has a male threaded piece attached to it. The pipe coming out of the ptrap, do I need to buy a female thread and attach it to the pipe before threading the two together?

Thanks!

I can't help with cutting your counter top but I can help with the plumbing.

how do I secure slip joint extension tube to the pipe that runs out of bottom of sink? And, the extension pipe going into the ptrap seems to just sit in there, is that right? Do I need to use plumbers putty or any other adhesive when joining the pipes?
All the connections will be slip joint,(compression joint) connections. The tailpiece going into the top of the trap will also have a compression nut and gasket on the "P" trap.

the house drain pipe coming out of the wall is pvc and has a male threaded piece attached to it. The pipe coming out of the ptrap, do I need to buy a female thread and attach it to the pipe before threading the two together?
This is the male half of a slip joint connection. You will need a compression nut and gasket to complete the fitting. Good luck, Tom

If the "granite guys" made incorrect cuts, and you have documentation, I would have them re-do it. Without the proper tools it's more difficult to enlarge a hole than to drill it from scratch, and you run the risk of destroying the entire piece.