My "A" bike has this type of braking system:
https://www.sheldonbrown.com/canti-direct.html

Yesterday, the noodle (?) became unhooked. I managed to pop it back in but I noticed the thing it clips into is bent, I mean the divet/hole it fits in. Also the front brake isn't working great, but the pads could be worn (had to get the rear ones replaced recently.)

Does the entire braking arm (?) have to be replaced, or can the little metal thing the "noodle" fits in just be replaced? How costly will this be?

*sigh*

i had a similar situation as yours last week and asked my lbs if i could replace just the tiny metal cage into which the noodle goes. lbs said no, you've to replace the entire part of the brake that touches the rim. in my case, he bent the cage back into shape. told me since this had to be done only once, not to worry mechanical stress (like bending a paperclip). a few days later i decided to replace that entire part anyway (wanted more clearance for fenders + i don't mess around with brakes). it cost me $25 for deore front brakes. o btw...why did this happen? my front wheel turned all the way back (kind of like a 180) and that twisted the cage.

so no, you cannot replace just the cage you have to replace the whole thing
that'll cost you $25 per brake
you can also just bend the cage back into shape if this is the first time it has happend
i am unreasonably paranoid about brakes so i 'wasted' the 25.

I think it happened when I put the bike in the laundry room somehow, that's my theory anyway. $25 + labour. Grumble. Oh well. I'm paranoid about brakes, too. I'm not sure just bending it back is such a good idea, what if it decides to snap or something when you use your brakes?

right i asked that to my lbs too. question for you - has this happened before? have you had issues with the cage? how bad was the bending? in my case, it happened only once and it wasn't too bad. my lbs inspected it and gave his reccomendation that i would be fine. he also told me that...when you brake and the noodle squeezes in, the cage feels force in the horizontal direction (perpendicular to the weels). it does not feel force in a way that will twist the cage in the vertical direction (which is how my cage got loose to begin with). under these particular circumstances, i said ok, cool. i was still able to find an excuse new brakes since i wanted more clearance for fenders.

on one hand i don't want to advise you to spend money when you don't need to. however, these are brakes, they save us from broken bones (just imagine a single mile without brakes ). being liberal with money on brakes can't be bad thing, can it? i can justify new brakes since you are having issues with your current one anyway. so its up to you. i say its only $25 - go ahead and get yourself a peace of mind. now if your lbs insists that you don't need to replace (like my lbs did) and you're cool with that then that's another option. i was about to do the latter but i kept getting paranoid and thinking about the rear brakes as back up. that frustration wasn't worth it for me.

The hole where the noodle goes is bent outwards a bit, warped kinda...does that make sense? The noodle doesn't sit completely right in there now. I wish I had a macro lens for my DSRL so I could show you.

no need because i know exactly what you mean. doesn't "sound" so bad. go ahead and put the cage back into shape or have your lbs give it a look. yes, that hole is now bigger because of the distortion but once the lbs twists it back - no worries.

Cool...thanks man!