If you understood the concepts as they apply to the NES it is not that much different for more or less anything, be it older or newer. Newer systems allow for more numbers and quicker manipulation thereof but data representation is still data representation.
If someone tells you the locations to those then it will possibly be pretty straight forward and you can get on with the act of tweaking them to your will -- my only reservation being that custom weapons are a thing there and those can be more weapon parts and custom stuff (even in shops/drops) rather than the more classic final fantasy clone where it likely is a big table somewhere of all the stats either in order of appearance in the game or for that unique identifier for that item. It could still be that fabrication is just a shop that takes monster bits as currency but for something as extensive as the Monster Hunter franchise... I would not make that bet. You can have both styles in the same game, and you can have a halfway house like base stats + buffs elsewhere.
Finding it when such things are unknown is a trickier prospect, though far from impossible. You can find such data without messing with assembly or the more hardcore stuff. I assume you have looked at file names already, and also eliminated based on file name/extension/size.
First step is look for the stats in memory with a cheat finder and then see if it is in the game somewhere. Stats are probably decimal on the screen so remember to convert to hex. The vast majority of the time games do things on a weapon by weapon (or component by component) basis rather than here is the table for attack values, here is the one for accuracy, here is the one for magic attack...
I doubt it will be some kind of XML setup here (I see that more in really involved PC western PC games) where it is a list of stats and extra effects to avoid having a each entry in a database list be 50 bytes long to account for every enchantment combo and strength thereof but it would not be the first time I have been surprised, and the game could benefit from it.
You can try corruption too. Find something that looks promising and fiddle with the numbers (this can include copy and pasting what looks like valid data over large chunks of the rest of the file), boot the game back up and see what changed. For something like this I doubt you will run into the bestiary issue -- in older games the list of monsters and their stats in some kind of end game or in game bestiary might be standard text rather than pulling from the same table the battles use, meaning a change of the battle stats might not be reflected in the bestiary and vice versa.
If the game changes between regions, and includes a rebalance, DLC weapons... then comparing that can be good, and for as much as they pumped these things out in Japan at least (I'll be nice) you can probably look at the sequels there as something quite viable to compare with, possibly different consoles of the same vintage if someone has taken a swing at one of those.
The class stuff can be a bit trickier but if it is that core a concept it might be in the game rather than something in the binary (this would be the eboot files on the PSP).
If you do want to do the assembly way then find the data in memory (if you have to start with a save then do that), reset the game and follow what path it takes to get there from a shop or smith when buying from then. That will also tell you how it generates stats.
As for me having interest then Monster Hunter on paper should be everything I want in a game (weapons creation, thoughtful combat, giant monsters, exploration) but in practice I find them so incredibly boring and tedious to play, and I really tried to get into them more than almost anything else I have ever done, so I am out there. I heard the more recent ones might have improved things but I have yet to try those.