I am extrememly unfamiliar with scripting, and was curious to know if you could write a script for a repair hammer that would either break, or fully repair an item (the % chance of happening doesn't matter)
if not that, then a more simplistic version that would just - no questions asked - repair whatever selected item fully.

Why?
I'm making a merchant mod who sells rather...different...but interesting items...they are all very costly, but, efficient for adventuring.

thank you!

Unfortunately, the function of the repair hammer is something which is hard coded and cannot be duplicated. Even if you make a straight copy of the repair hammer, the copy won't work directly. But, there is hope. What you can do instead is make an inventory item which records and adjusts the game settings related to the repair menu,
http://cs.elderscrolls.com/constwiki/index.php/FRepairSkillBreakBase <--was just added... as in now, so may not be correct or working.

Then creates a repair hammer (so the player has one to use) and uses the normal hammer (equipitem) to use the new settings. Once out of the repair menu (http://cs.elderscrolls.com/constwiki/index.php/MenuMode_%28Function%29) you revert the settings back to what they were before. You might want to do some other stuff, like making sure that the player doesn't gain/lose repair hammers which weren't used (eg; recording how many normal repair hammers the player has, and temporarily removing them while adding the same number of "special" repair hammers the player has as normal repair hammers to be used, and then reverting back). Just be aware that you can't have a scripted object remove itself from inventory, so you should probably use a quest script to manage most of this swapping, adjusting, and removal stuff.

thank you (and please excuse any poor spelling, I am typing in the dark.)

Unfortunately, that didn't make much sense, because, liek I said, I am EXTREMEMLY unfamiliar with scripting. I couldn't write a script for the life of me. (not even scripting a quest)

~and before you send me off to wikis, yes I have read them...but I have had issues grasping the information.

Check out some of the tutorials and such on TESA. Link in my sig.