Milling rough stock from your own lumber can be rewarding and cost saving in the long run. However there are some upfront costs, time investment and you usually need some space to store lumber for drying and keeping.
Unless you're planing to use it regularly for some years, it might be worth to commission someone with a portable mill.
Those are chainsaw attachments that are clamped to the bar. You're referencing from a fixed distance to the bar to determine the thickness of the resulting board. A ladder or other straight and twist-free implement is required to get a good first cut you can then reference from for subsequent cuts. There are different guide/bar length options that determine how thick of a log can be cut with it. The system is fairly compact.
It is recommended to use a chainsaw that has a bit more power than what would usually be used for trimming or cutting small trees. The Stihl 660 or 880 are often used.
Other recommendations include 1) a thinner bar with dedicated rip chains which requires less material to be cut and thus cut faster and reduce wasted wood. 2) a winch that is attached to the mill and uses a fixed point in the direction of the end of the log which makes for a more continuous and smoother cut as well as saving one from lifting and pushing the saw.
That the chain should be as sharp as possible should be self-evident.
Logosol offers various sawmill systems that can be transported to where you cut trees and mill your lumber on the premises. They are fairly expensive but overall well regarded. There are chainsaw based and bandsaw based types, the main difference to the Alaskan ones is that the saw runs on a platform or beam.