This tutorial by Ben Mathis can help you merge your detail normal with your highpoly source normal. http://www.poopinmymouth.com/tutorial/normal_workflow_3.htm
Nice :) . Just follow the tutorials. It will get your through it pretty painless if you haven't worked with UDK. Just lots of checking the tutorial and then back to the editor :)
Seriously, search around. There are lots of Modo tutorials out there. Here's 12,000 videos to get you started. :) https://www.youtube.com/results?search_query=modo+tutorial+beginner