lets hope you don't take a year to build your 4*, its not that complicated of a build,couple of months a little more if you are a slow builder.
here's a suggestion for dad, have him help you build a really flat building surface,it doesn't need to be too big just enough for your plans to fit I use a reenforced piece of plywood with hinges screwed to the wall so when I am not working there it folds down out of the way.
with a shelf to put your finished parts out of the way on untill your ready for the final assembly.
of course, I am the dad, so the garage work area is mine LOL.
your dad has a good point focus on the trainer and show him your ready to build, no doubt you will have to do some repair on the trainer, and you will gain some building expierence along the way to your learning to fly.