I see a lot of people (well, "a lot" not really I guess...) doing these sorts of systems and I have to wonder, do you all have ME/EE degrees or something? I have a Physics background which meant a lot of lab work, but I think I'd probably shock myself or blow myself up if I was trying to mess with all this stuff. You're using solenoids for the gas control on the burners, right? I would love to build a system like this, but have no idea where to start (parts lists are helpful if you know where to get them)...
Well, it is a lot of trial and error, for sure. But if you have a healthy respect for the powers of electricity and gas, chances are you won't blow yourself up. You need to be aware of the inherent dangers in doing something like this, but IMO the reward of having such a system that you built yourself outweigh everything.
As for parts lists: it's tricky, since everybody has a different idea what their system should be like. I work as a software engineer from home, so I have a lot of time browsing the forums and piecing together information. Some people have attempted complete write-ups, but I found I picked only bits and pieces that fit my idea of the ideal rig. Electric or gas, portable, stationary, low pressure, high pressure, NG, fully automated, bare bones, PID controllers or computer, pilots or electric ignition, the list is endless. I know it's daunting.
I think I will write up some of the design decisions, together with what I would do differently, but my brew pipeline is empty, so filling up my keezer comes first ;-) I'll post here when I'm ready.
As for the skills needed: if you don't have the welding abilities, outsource. There's plenty of good welders out there, find someone with references and check them out. I had a horrible time with the first guy: unreliable, not really great with stainless and dishonest about his work. My stand turned out pretty crooked, and i didn't even trust his word about pressure testing the gas beam, so I had that re-done. The stand alone ended being over $1K, which in hindsight is horrible, but I had to throw good money after bad. So yeah, check out your fabricators.
The electric side I had no problems with. The BrewTroller is not for the faint of heart, but the guys on the forum are very helpful and forthcoming. I have half an EE degree and remember receiving a soldering iron for my ninth birthday, so yeah, I would say, that was the easy part. I did the wiring diagrams in my head. Get help if you don't feel comfortable. You can wait with the high voltage stuff until you're ready with all the other wiring and dry-run the solenoids, sensors etc. until you feel comfortable, then enlist the help of someone with electrical knowledge to hook up the rest. No risk of electrocution there.
The gas side I was most afraid of, but it turned out to be fairly straightforward. Be diligent, read all the manuals that come with the valves and pilots, and check for leaks with soapy water.
It costs a lot of money, for sure. I'm afraid to tally it all up, and not just the big ticket items like valves and burners, but also the small stuff. It's a serious obsession, not just a hobby.
And if it blows up, don't blame me.