School me on hydraulic components

[JDH429]

I hate to sound like the kid who wonders into the middle of the movie and asks what's going on but... I'm very interested in building an excavator. Its what has drawn me to this forum. I've been doing all the research and am unsure about what avenue to take.. Im new to rc Construction and esp hydraulically powered. One direction to go is to purchase a Rtr like the rc4wd 4200xl. I can learn the ins and outs and what makes one run. I've heard both sides of the story on this unit.. So im aware its not the greatest but i simply cant justify spending the money that the main stream units cost. One plus is its affordable and would be a cheaper way to get acquainted with this type of machine. There are some pretty convincing YouTube vids on this digger recently that Digginwithmartin has posted that make it sound like this machine has come a long way and the bugs have been worked out.
The other ave. is to just start from scratch, buy a Bruder, prototype, work out the system and go from there replicating and fabbing metal parts based on that model. However I have no experience with the hydr systems or who and what is the right choice. Actually I wouldn't mind if someone could chime in and explain the hydraulic system components that go into an excavator. What radio equipment is typically used as well. I've seen the guys who machine their own valve blocks and pumps and that simply awesome and my hats off to them but I'm not quite there yet. I am fully capable of machining and fabricating the majority of a machine tho and look forward to the build, but a Rtr for a few hundred more than what I may end up spending to fully equip a home brewed model isn't terrible either. I hate to sound like I'm asking for the short quick answer from people who have spent countless hrs building their own machines and figuring out the problems alone. I guess if I go the build from scratch way I want to make sure I completely understand what is needed and how it all works first. So I know a Pump is needed, a valve block, cylinders is needed but what else and what specifically should I be looking at if there is a best route to take as far as brands and methods. I just dont feel like i know enough to start and want to get to that point asap. Thank you for taking the time to explain things that may seem elementary to you but for a new guy believe me it's overwhelming.