I made every piece of this except the glass and I assure you it could look so, so much worse than it does. I custom ordered the glass so as to use as much of the existing hole in the siding as possible - this custom fit is why I spent the time to make a window frame from scratch.
Prepped hole in the house with blocks in place and nailed down to support the base of the frame. The existing exterior facing was left in to make sure the frame couldn't fall outwards. I admit I was very tense when we picked up the window and started moving it - I had spent better than two full days making that frame and I did NOT want to lose it. Aside from the cat trying to trip Ana there was little drama in actually moving it.
This is with the window in place, shimmed, leveled, and fastened in place. It looks crooked - it is not. The framing below it is a little down to one side, but the framing will be invisible with the wall back on. I checked many times. As planned, nobody on the outside can see into the shower area any more and we have a dramatically larger window (~25% larger in square inches but also without crossbars) than before to let in more light. This time it's centered, which is a major plus. It should be noted that with the old window there were blinds that always had to be on, which have been forever banished. Win!
There is definitely some priming, painting, caulking, and cleanup work to do on the exterior but overall I would say it does not look screwed up. There are a couple of sizable gaps but this part of the exterior faces the neighbors and is never seen so I'm OK with somewhat rougher work here. Success!