Well, I can tell you what I did, and see if that helps. I've played that map so many times I've practically got it memorized.
You start in the northwest corner. Send a halfling north, because just the other side of a hill there's a "seeking refuge" unit waiting for you. Everyone else heads southeast. Everyone you get from refugee stacks, send them to the limit of their movement south and east, grabbing farms, a tower, heading toward that life node. By Day 2, your leader should be able to get to the 2-hex city on the south road, and one unit should be able to get the life node by day 3 for you. I grab the city near the mid-map bridge early, and just fortify it, usually with slingers, swordsmen and the cleric you get.
All the pony riders head along the south road. There's a pile of gold to the west of the road, south of the 2-hex city - grab it. There are some more troops along there as well. Take the whole kit and kaboodle south with you, and don't bother leaving anyone to guard - you'll need them for those elven towns that are being attacked by the goblins. If you can get down there really quickly, you can drive out the goblins that are there, and sticking two stacks at the bridge will stop attacks, since the opponent can't bring more than one stack to bear at a time.
Build slingers and elven archers, ignoring others. Don't worry about upgrading, since level 2 units won't help that much. Maybe add walls to the towns closest to the bridges, but otherwise don't bother. Send an extraneous unit along the pass to the elven town in the southeast corner - it's unlikely the goblins will attack it, since it's got some units defending it and walls. Consolidate, take a force and get what you can out of the ruins west of the elven villages, build a couple of battering rams, then, when you've got 12 or so units ready to go, head across the south bridge into Goblin territory. Once you're taking the battle to the enemy, things should go well. Remember that your ultimate goal is just to kill the goblin leader (and that the only way you can lose is to have your leader die).
This isn't the only way to approach the scenario, but it works, and usually doesn't take that long. Your leader can get only two levels in the scenario, so go ahead and work on getting that experience.
Your problem may be dealing with tactical combat. Look for hints on how to handle it. As a human player, you should be able to destroy superior AI forces in tactical combat, as long as you are careful and load up on missile weapons. The AI "damn the torpedoes" approach doesn't work all that well...