You won't have to change the tripod legs. Arca-Swiss is simply a type of clamp & plate system that allows a quick and very secure way to attach and remove photo accessories. Typically, you'll see an Arca-Swiss plate on a camera body or long telephoto lens ring and an Arca-Swiss clamp on a ballhead. There are two types of Arca-Swiss clamps: 1) screw and 2) quick-release. I have had both and personally prefer the quick release type. It works with a spring-loaded lever that pushes the clamp shut and locks it. The screw type needs to be turned in order to tighten or loosen the clamp onto the plate. Both are effective and secure - it's really a matter of personal preference.
Often, you can just change the clamp on your ballhead. However, there are ballheads that have the clamp permanently attached, so it won't be possible to just change the clamp. In that case, you will have to purchase a new ballhead that either already has an Arca-Swiss type clamp, or a ballhead without a clamp that will accept an Arca-Swiss clamp.
The cool thing about Arca-Swiss is the interchangeability of accessories. In other words, if you have a flash arm or other accessory, you can put an Arca-Swiss plate or clamp and use it with other components in the system. I leave all my clamps and plates attached to every accessory and am able to freely interchange all my accessories.
The cool thing about the L-plate on a camera body is the quick and easy flipping of the camera body onto a ballhead for vertical shots. It's very easy to unlock the Arca-Swiss clamp, remove the camera and flip it vertically, then secure it to the clamp in a vertical position. For those that work with tripods on a regular basis, it really helps and keeps the camera centered on the tripod for greater stability, instead of flipping the ballhead on its side and have the camera "hang" over the side of the tripod legs, especially when using long and heavy lenses.
The initial investment into Arca-Swiss components can be pretty big. Therefore, unless you don't have a system in place or you really need the convenience of Arca-Swiss, it may not be worth the investment. Manfrotto has a good system and many professional prefer it over the Arca-Swiss system. I've never had anything other than Arca-Swiss, so when I started my system 20 years ago, I started with the Arca Swiss B-1 ballhead and a RRS plate - RRS had just gotten started then.
This is one of the photos I sent you by PM. Notice the quick release clamp on the ballhead. The quick release lever is located on the ballhead clamp underneath the lens, towards the front of the camera body. Notice the screw clamp on the Kirk clamp attached to the flash arm on the side of the camera L-plate. Both are very secure.
I hope this helps.
The ability to switch between landscape and portrait orientation is the reason I did it..
