I am curious to how difficult it is to manual focus at farther focal lengths such as 200-300mm especially on my d3200. So in the end should I opt for a 55-200 AF with VR or challenge my skills and shoot manually with the sigma?

Manual focus is an acquired skill. It's one that takes lots of practice. Ultimately some folks find it easier or harder to do than others do. It's hard to say how hard you will find it to be.

Back when I started we learned to manually focus because we had to. There was no other way to focus our SLRs. Other than astro work and occasional landscape or architectural work, all of static scenes done from a tripod mounted camera, I haven't voluntarily manually focused a shot in decades.

By using a modern Digital SLR designed for use with autofocus lenses, though, you'll be at a distinct disadvantage compared to us grizzled old-timers that learned manual focus on cameras designed to be manually focused.

• The viewfinders of pre-AF cameras tended to be larger and brighter than their modern AF counterparts, even on consumer grade cameras. Now only the top pro models tend to have large, bright viewfinders that were more commonplace in the pre-AF era. Even those top end DSLRs don't have VFs as bright and large as some of the top tier pre-AF 35mm cameras did.
• The viewfinders included manual focus aids not included in DSLRs and other ILCs with AF capability. Split prisms and/or prism collar micro screens were common in SLRs before AF came along. Some cameras had one or the other. Many cameras had both. Other types of cameras often incorporated a parallax rangefinder type of focusing aid.
• Lenses were also designed to allow finer gradations of focus adjustment. Focus rings on lenses had to be rotated much further to get the same change in focus position that now results from a very small movement with current lenses.

The only thing some DSLRs offer that we didn't have back then is the AF confirmation light, but on many cameras the focus confirmation light has a fairly wide range of tolerance that will tell you a subject is in focus when it's actually anywhere between slightly front and slightly back focused.

I certainly wouldn't want to try to do it today with a moving subject without at least a split prism in the center of the viewfinder. I'm not even sure if my younger self thirty years ago, when I was fairly competent using manual focus with the advantages of brighter VFs, focusing aids, and long throw lenses (and my eyes were also better), could have been able to do it with dimmer VFs, no focusing aids, and short throw lenses without a LOT of additional practice, if ever.