I think that it may be best to give both the script and the game file. Just so that the proof reader/copy editor has a deeper understanding of the kind of story you wish to create. It's all well and good that they will spot your spelling mistakes or grammatical errors and help in that aspect, but you have to make sure that they are not trying to change more than they should (which you probably know), so trust is a key factor here.
Uh, I am also pretty sure that most people on the lemma soft forums will not wish to be contacted by phone... The most common (I would have thought) would be e-mail or IM. IM would be preferable if a ton of questions were needed to be asked and quick answers equally needed.
Timeline is always tricky. As so many factors need to be accounted for. The editors skill/time available, for one.
The best way is to tell them how many words there are in the whole script and send a sample of your writing to the editor so that they can assess your abilities to see the amount of work that needs to be done. Then they will be able to give a rough estimate of how long it will take, and stick to that time. (I have met people that can edit 500,000 words in a weekend, so if someone is saying it'll take weeks for them to do a 50,000 word project my advice is to find someone more willing to work or has more free time).
And I think that's all you asked for. I wouldn't say they were rules. Just helpful tidbits. Well. I hope it's helpful. And I apologise if I made any spelling mistakes or the like. I am extremely tired