Scenario Difficulty Rating System?...and other ?'s

[Pepper]

Your mentioning spider holes reminded me that the USMC campaign can be a little tricky.
Try to get Kiowa down to work. Thats a good intro.
Play Wild Bill's "Over There" its a really small scenario, again it will force you to focus on small squad tactics.
Double Deuce's drug war campaign is also an excellent suggestion. In fact that campaign is probably a little better for starters than Silver Lions.
I'd mostly suggest playing the small scenarios, and play them over and over until you learn the basic tactics of engagement. Then play the larger scenarios and campaigns.