I am a new adopter of linuxcnc (I have dabbled for years, but I would say that it's setup is now easier than it ever was. that is not to say it is simple, just easier)
I have come the route of mach3, mach4, uccnc to linuxcnc. usb smooth stepper, ethernet smooth stepper, uc400eth, uc300eth +ub1+ud1. to say I have spent a lot on hardware is an understatement.
to answer your questions.
1) the uc100 is not compatible with linuxcnc, the rest of your setup will be.
the uc100 is a usb to parallel port (lpt / db25 ) motion controller, which means if your pc has an lpt (printer port) you could run linuxcnc without buying more hardware (possibly!)
given you have a uc100, you probably don't have a printer port on your pc..... probably ...
it is generally not recommended to run linuxcnc on a laptop, but you could always test your hardware and know for sure by booting up your hardware using the linuxcnc iso live install burnt onto a DVD or usb memory stick (download the linuxcnc iso, download RUFUS (one option, there are others search " iso bootable USB" on Google))
once you boot the live image of linuxcnc run the latency test and post your numbers.
to improve your numbers, go into your bios (f2/F10/ delete at start of boot) and disable all energy saving / speed throttling / power management settings.
if you have an lpt / printer port and your latency numbers are good you can use linuxcnc without more hardware, if they are not so good, then you can buy MESA hardware to offload some of the processor load of running linuxcnc.
if you have an ethernet port, then ethernet hardware would be best, given at some point you will want to change your pc and it will probably be more forward compatible than PCI / pcie cards in my opinion.
I have only ever played with MESA hardware as I don't have an lpt port.
2) linuxcnc is different, it has a learning curve. if you have a simple setup and are happy to just run AXIS as default for a mill then I'm sure you could be up an running in minutes using the MESA Pncconf utility walk through.
linuxcnc offers other modules?? to add stuff like pendants and Native am which expand its functionality, but require additional configuration steps and understanding, but walkthroughs are available.
(I am at this stage of understanding about adding other stuff and setting up my other hardware )
3) someone has already offered to help you, plus just ask on the forum.
be specific about what you are asking and provide as much info as possible (eg if it throws an error, post the error, don't just say it doesn't start or work!!)
only you know your hardware and how you have wired it up and set it up, and there are probably millions of possible hardware setups and infinite options on configuration.
