I would love to start doing some stitching in nature photography (to immitate my old Xpan pictures).
How do I start?
Start simple, and as you gain an understanding of some issues that may prevent a perfect stitch, you can add components to your setup to solve those issues.
You can start with your current gear+tripod. Then you need Panorama stitching software, e.g. Photoshop if you already have that, or a more dedicated software that allows to intervene when things do not line up as intended. You can start with a free stitching program like Hugin
You will learn that it is necessary to add some hardware to successfully avoid parallax issues that would otherwise prevent you from lining-up both foreground and
background features in the overlap between images at the same time. This becomes more apparent when you include detailed foreground features. You need to shift the camera into a position that allows you to rotate the camera around the axis through the entry pupil of your lens, a rotation that's usually called Yaw. When the camera's tripod socket is aligned exactly underneath the optical axis line, then you only need some hardware to shift the camera back (or forward) in order to allow horizontal rotation of the camera/lens through the lens' entry pupil position, AKA the no-parallax point (NPP). When the camera's tripod socket is offset to one side relative to the optical axis line, then you need additional hardware to solve that issue.
When you want to expand from horizontal stitches to multirow stitcches, then additional hardware is required.
When you intend to do panoramas on a regular basis, it is wise to invest in a modular set of hardware additions that can be expanded as the complexity of the required setup increases, instead of having to buy completely new hardware. While not cheap, the Really Right Stuff materials offer good quality and they have several sets specifically intended for panoramas such as their Pano-Elements-Package
(the URL link seems to be broken currently).