I have a suggestion for you to consider. It's good that you are realistic about your skills and experience, but I also agree that putting together a DAW is not rocket science, and possible for all but the most technology challenged. Usually the only tool you need is a screwdriver. The connectors are all keyed so that they can't be plugged in wrong, and the actual putting it together really is very easy - and fun. The hardest part is setting up partitions on your drives, loading and configuring windows, and installing the various drivers for your hardware. But if you get stuck on that, the worst that could happen is that you have to pay a local computer shop a couple hours of thier rate to do it for you. You'd still be money ahead by quite a bit.
Then there's the question of what happens when your DAW has a problem up the road. If you built it, you can probably fix it. If you have it built for you, it will be this black box that you'll have no idea what to do with except send it off to the place that built it for you, and wait, and wait.....and wait for it to come back.
Finally, the computer is just the part of your recording rig that crunches numbers. It has nothing to do with the sound of your recordings. That's all in the converters, preamps, mics, monitors, cables, software, plugins, etc.
I have no Idea what your financial resources are, but I hate to see people shoot their wad on thier totally awesome computer, and have nothing left to spend on the things that really matter to the sound. So keep that in mind.
Regards,
RD