Thanks for the answers.
With NBD's points above and some more time in the game I can provide some more answers:
1. The quest needs you to finish your first set of stone walls, this took me quite a while. You also need an alliance, I'll get to this later.
2. Still not sure on this one but Hi1zone's post in general gives you some good tips for farming resources.
3. As NBD said, Elves don't need to bother but if you are using Dwarven miners then I suggest hiring some human resource cart mercs and parking them next to the mining node.
4. Doesn't seem to be possible, I can only hire mercs in human, Orc and Elven lands.
I've also found out some other points that almost everyone will know but new people like me might find useful, spoilers, sort of, below:
1. To get an alliance with an NPC city you need a relation score of +5, you get this by giving gifts in the diplomacy screen, I got the following:
- Gift of 1500 gold = +2 relations = trade agreement
- further gift of 2500 gold = +3 relations giving a total of +5 = alliance
2. You can farm NPCs on the world map by pressing the magnifying glass icon, you need to be out of range of cities. This takes you to a tactical map with various friendly and enemy encampments and patrols. Some regions give good experience, others like wolves give good early gold. Use these to train your elite units as well as your normal units.
3. You can hire other species mercs in any town you have a trade agreement.
4. Treants, Orcs and resource carts all carry 500 resources each, more than the 200 for Wardens.
5. You can send resources to anyone you are friends with, this doesn't seem to take a trade caravan but I suggest it should.
6. Be very careful with special units, if they die then are gone for good.
7. If your leader dies he will respawn at level 1, use the NPC farming to train him up to help him survive.
Do any mods think it would be good to have a hints and tips stickie?