Hello and welcome!
Be aware that this post is just to provide a general idea of the process without having to read through pages and pages of installation guides - for detailed and reviewed information, still read those guides.
I'll start off by briefly answering your questions to provide a general overview:
- Yes you can keep everything intact
- Yes you will easily be able to access all your window data from within linux
- No you won't have to unplug the drive in order to choose which operating system to boot
- Basically: Just go ahead and install Manjaro on your new SSD, the rest will simply just work™
The fact that you've decided to install Manjaro on a completely separate drive makes everything much easier and safer for beginners, but fyi it wouldn't have even been necessary (in case you didn't know that). However, as we all know, more disk space is more better
The installation process will be as easy as booting the installation ISO and telling the installer to through the whole system onto your newly bought SSD, the rest of the system should remain untouched.
One important point to note while the setup is where to install the bootloader (GRUB). Because you have a separate drive for Manjaro, I would highly suggest installing the bootloader onto that one and leaving everything Windows related completely alone, just to be safe.
(Again, there are ways to make them two work together nicely if you have to, but from my experiences it's easier and safer for a beginner to not do that. Don't wanna risk accidentally trashing your Windows installation as restoring that one is much harder than restoring any unbootable linux system.)
Once the installation is done, you can set the new SSD as the default boot drive in your BIOS settings and it should already present you with a nice and convenient selection menu to choose whether to boot into Windows or Manjaro.
That way you still have the option to simply choose to boot Window by bringing up the BIOS's boot device selection if things go backwards and Manjaro is unbootable.