This is a question you will be able to answer only after you have torn down your transmission, cleaned and inspected the parts.
Richard Grace suggests, “the minimum parts replacement would have to be a Small Parts Kit which includes main drive gear rollers, thrust washers, synchronizer dogs and springs. One other almost necessity is mainline bearings.”
Of course you will want a new clutch disk and throw-out bearing (you might consider a new pressure plate as well). So for a minimum investment (perhaps as little as $50, not including clutch disk and pressure plate) you could have a rebuilt transmission ready to install in your jeep. Anyway a lot less than a so called rebuilt transmission from a vendor and you will have the satisfaction of knowing you did it yourself. You will need to add to your costs any defective or out of tolerance parts that you find during the cleaning and inspection process.
For much more about the WW2 jeep transmission, T-84J, check out my book – Trouble Shooting And Rebuilding The T-84J. This book, written by me, will take you through the process step by step–with lots of pictures!