Definitely ask for the course syllabus ahead of time and determine whether it's applicable to you. In my experience these courses are great at teaching you the particulars of how to craft makeshift splits, crutches, stretchers, etc., how to correctly apply bandages to a variety of wounds, how to recognize life threatening injuries or conditions, and how to deal with some of them (like tourniquets, hypothermia/heat stroke, recognizing and using an EpiPen). You can get a lot of good information from free or cheap first aid books and websites but it can be helpful to have someone show you how to make a sling, for example, and correct your technique.. that's where the benefit of the courses lies. If you don't need the hands on then you probably don't need the course.
For what it's worth my plan in an emergency is usually to stabilize the injury well enough either to move yourself to the car, or to stay alive long enough for rescue to arrive. Most injuries are not life threatening, or at least not immediately life threatening. You're going to be limited by what you're willing to carry with you in your everyday kit, so don't bother learning any first aid techniques if you're not willing to fill your bag with the gear to implement them. For instance if you want to brace a broken leg but your kit doesn't have enough rope or strong tape. There are a lot of free resources online that can help figure out what you need in your own kit.
ETA: My experience is with a variety of training programs through the Boy Scouts (don't remember all the names - they drilled this stuff in us pretty hard though!) and annual Red Cross first aid training through a previous employer (can't remember if this was a one day course or two days).