Joe,
You will find that most firms hire people for their particular needs. If they need someone with grading skills then illustrating capabilities would not help. If they need a Manager then he would supervise an illustrator. Get the picture?
If you can find the money, take one of Richard Scott’s Color Mastery courses. As a student of his I find his techniques quick and very effective. Will change your life! Money well spent!!!
I wouldn’t waste time on a MLA at this point in time. Experience with a firm will be time better spent.
A few books you should own are: Color Drawing by Doyle, Plan Graphics by Walker and Perspective Sketches by Walker.
You can always pick someone’s techniques and just master them.
SketchUp is pretty easy but, I much rather see someone draw their concepts by hand.
Good luck,
stephen carreker, asla