The brakes are pretty easy to replace. Remove bolts holding the housing on (maybe 5..??) then remove the nut from the adjuster stud, and the unit will pull off. Could be the expander plates and ball bearings are rusty, and not activating. You can clean up the plates. The bearings can be cleaned up, if not too bad, or replaced if rusty and grooved. The springs that hold the plates together can be iffy. If they are pretty rusty, they may break when removing. Brake disc's are probably worn and glazed.
Here is an exploded view of the brake mechanism, from the Case/IH online parts store:
Official Case IH Online Parts Store and Case IH Catalog for Best Parts Search and Best Parts Look Up. Case IH Parts for Case IH Tractors, Case IH Combines, Case IH Tractors, Case IH Manuals, Case IH Parts If there is differential oil seeping around the edges of the brake housing, and has the disc's oil soaked, the seal will need replaced. You'l need to check the condition of the bearing and race too. I'm not seeing one in the exploded view, so someone more familiar with the B414 can enlighten you on that. I'm just familiar with that style brake system, as it is used on a lot of IH tractors. According to the parts book, there are 2 different sizes of brake discs, so you'll need to measure, and see what size yours are.
For any part on your tractor, go here:
Official Case IH Online Parts Store and Case IH Catalog for Best Parts Search and Best Parts Look Up. Case IH Parts for Case IH Tractors, Case IH Combines, Case IH Tractors, Case IH Manuals, Case IH Parts I've already got it to the B414 Diesel manual, so all you need to do is select a component.
If you go to Messicks:
Case Parts | Messick's You can enter you model number in the provided block at top left. You 'll get the same exploded displays, along with part numbers, but you'll also get the price of selected part at any Case/IH dealer. You can also do some comparison shopping by copying the part number, the paste it to a search engine. I've had the best luck with Google.