The first input jack in my Valveking broke off, the plastic part sticking out came off when I was plugging in my guitar. I used the second input and it worked, but now I'm not sure what to do. Can I just glue the bit that broke off onto the amp, or do I have to replace the whole input thing? I would just take it to a tech as it's still under warranty, but I have a gig in six days, and the last time I had a problem it took them a while. Thoughts?
try plugging into it, if it doesnt work, then you need to open it up and re solder it.
30 mins tops
what plastic part?

it should just be the jack sticking through with a nut on it

open it up, stick the jack through the hole, put the nut on, and then close it back up.
if it works, then get by til the gig or fix it yourself.

it is a little unclear as what your problem is exactly, but it sounds like the plastic nut on the outside broke or came undone. you can get another nut (they may have one and give it to you for free if you frequent a cool shop), pull the head chassis, stick the jack through and secure it with the new nut.

or if you are just really uncomfortable (or the problem isn't that simple) then you can just take it in and have the tech mess with it.

either way, you need an amp for that gig, and if it works fine, then use it that way til the gig and then fix it. if it's acting up then you need to take care of it cuz you don't want crackles and pops during your gig.

in a worse case scenario (if the amp is ungigable) and needs fixing and they take a long time, then rent a loaner for the gig.
punk isn't dead, it's always smelled that way.

"A perfection of means, and confusion of aims, seems to be our main problem."
i think what happened was somethign caused the cable to be pushed, and the plastic nut got broken off, and the jack's solder points broke off
i was assuming the solder connections were secure because he said the 2nd input worked fine. those are usually wired in parallel and if the solder connections went i would assume some grounding out would occur (but he reports no problems).

but i am only guessing.
punk isn't dead, it's always smelled that way.

"A perfection of means, and confusion of aims, seems to be our main problem."
Okay, thanks for the replies. I just plugged into the first input and I guess the solder points are fine. It sounds normal, and since I use a headphone jack in the first input it should be fine for the gig, but I was planning to sell this amp after the gig and I'd like to honestly say that it's in perfect condition.

it looks basically like this

but with the jack broken off pretty much flush with the board. (The picture is just something I pulled off google images, don't have a camera here) Can I repair this without soldering?
the actual barrel of the jack broke off? if it did and it still works then it doesnt matter i guess, but you can order a new jack for like $3 and solder it in, and its good as new
Does it matter what kind of jack I use? And is there a guide somewhere on how to open the amp, what to solder, etc.?