Game is kicking my ass on the first mission and I've yet to find any way of decreasing the difficulty.

There is no way to manually decrease or increase difficulty, you have to get gud.

Maybe this helps:
http://www.heroesofmightandmagic.com/heroes2/hintsandtips.shtml

This is the correct place for your thread:

https://www.gog.com/forum/heroes_of_might_and_magic_series

But off the top of my head, hire 2 extra heroes in the first week, and two extra heroes in the second week, consolidate the troops into one main hero and use the remaining 4 heroes for scouting/resource collection, and make sure to break through the main chokepoint at least early Week 2. Build the statue ASAP, the well by the end of week 1, and aim to build some good creature generators by the end of Week 1 too so on Week 2 Day 1 you have some solid troops to hire and add to your collection.