Not really, you just need to pay attention and be careful. The MII stuff all hangs off the crossmember, so as long as you get the crossmember in there square and straight, it's a cake walk.

If you're gonna do it in your garage, read this paper I wrote on constructing a flat and level surface for cheap on which to start your project....
http://streetmachinesoftablerock.com...opic.php?t=425