I think I used too few words in my explanation of Darcy not requiring help .. what I meant was that Darcy's abilities were such that he would be able to direct and organise the arrangements between Lydia and Wickham, including a commission for Wickham, without asking others for advice regarding the next step. The best description for this would be to act as project manager.

I was not suggesting that he might not need others to perform certain tasks (eg lawyers, agents or friends as already suggested). How I saw this working would be, for example, that once a commission was suggested Darcy would understand the structure and advantages/disadvantages etc of the militia versus the regulars (eg pay, location, regiments etc) and would also be aware of who he could approach to progress the issue.