Sounds a LOT like dysgraphia/dyslexia as it exhibited in my son, now 12.
You've already received great advice, so I'll only add a couple of things. Make sure the neuropsych is experienced in testing 2E kids. We had a terrible experience over the summer, so finding one that will recognize what is Giftedness, what is LD, and accommodate testing methods to fit is going to be a huge benefit in creating useful results.
The second is that while some of these challenges will be lifelong, many are developmental delays. We've seen huge strides this year in quality of written output, speed of output. He still can't spell and doesn't have all of his math facts down but has gotten much faster at using the few he's memorized and counting up or down. So what you see as overwhelming now may not be so overwhelming in a few years.
