No, it's pretty simple, especially if you've soldered things before. I've assembled three of them now and the last one took me maybe 5 hours total to do. I set a card table up in the living room and worked on it after work while watching TV or a movie. The trickiest part is a few connections are very close to each other, so take care that they are not bridged, and having some copper solder wick to undo connections is handy.
My work station. The laptop has the assembly instructions on the screen (http://www.megamanual.com/ms2/V3assemble.htm) This is very much like LEGO's for adults.
First night, after setting up the table, etc. And actually nothing here is soldered yet, just pieces put in place.
Second night.
Third night done with a MegaSquirt 3 and expander board. This is the unit in my Firebird today.
The bottom side. The black and white wires are the 4 idle control wires.
The deal that I think is great about assembling it yourself is how much you learn about it's construction. The directions are set up so you assemble it essentially by circuit type. Power, communication, intake and coolant temp, Spark, Fuel, MAP and accessory inputs. So if something is wrong with one of the inputs, you know where to look on the board (and refer back to the assembly manual). If you read my thread, and I mis-wired my alternator on my Firebird (always wire it directly to the battery!!) and I fried my Megasquirt's power system. I opened the case, checked the power circuit's components with a simple digital multi-meter, replaced a couple capacitors and diodes, and I was back in action. I knew exactly where to trouble shoot. Having a relay board on my Firebird probably would of prevented the toasting of my MegaSquirt. I like the extra layer of protection the relay board provides.
The key take away is, this isn't rocket science. One thing though is, if you solder it yourself, you'll want to purchase one of the Stim/Jim Stim's too. Which is additional costs. If you plan on possibly doing more than one build, its worth getting the stim, if you think this will be the only megasquirt you'll likely ever use, it may be worth saving your money on the stim and put it towards a pre-built unit. I've built three, so the cost of the stim has been amortized over three units and I'll probably build at least one more if not two (my Centurion, and possibly one other car). Or if you don't mind the cost, I recommend assembling it yourself.
