Built a CadPlans 1XXX, can't remember their model # anymore, and building this way has its pluses and minuses. If you know how to weld or want to learn to weld it's a great project. If you know how to do some machining then it's a great project. If you don't know how to do the machining get a kit. Building the mounts is the most important part of the project. Done wrong you can damage the tractor, but this is not likely. Also done poorly your FEL may never be straight. The rest of the project falls into place after this is done. Hydraulic cylinders and valves are also important. if you get a kit then also get the hydraulics with it. Saving $ here is not easy, and fitting other cylinders can be a pain.
If you finish you will be VERY familiar with how your FEL works. knowing something about welding, hydraulics, and machining are not bad things at all. Bottom line: If you have the tools and knowledge it is a fairly easy project. If you want an excuse to get the tools, (welder, drill press, grinder, etc.) then it is a good start up project. You won't save $ if you don't have the welder, drill press, etc, but it is an excellent reason to get these things.
Use my FEL all the time. Have used the tools that were required to build FEL many times over. Would do it again.