1) If I submit a tab request, how long does that typically take?
1b) If I had it in mind to speed up the process by say just paying someone for their time, how would I go about that?

2) Who is doing the actual work to write out said tab and what assurance do I have that they are competent at what they do? (Not that I've any complaints about the accuracy of any of the tabs I've found on UG, I'm just curious).
1 - you'll have to wait until someone submits a tab for your request

1b - pretty sure you could try and train your ear to figure out some parts yourself and save money. Personally I don't know who you could pay. Possibly look for a local musicia or teacher to help you out.

2 - Any registered member of UG can contribute. The only way to judges ones 'tab' is the view count and rating though its all down to personal preference