Price will vary depending on your location and whether or not there is a competent person with all the of the necessary equipment to do the work correctly. The cost of one of the those radios these days that is in used working condition is most likely about $30-$60 at most.
I am not saying not to get it reworked and fixed, but it will cost as much or more than the radio is worth is what others are trying to tell you. If you have a good local tech, and he knows you, maybe not, but otherwise, look into another radio and just use the Cobra 25 the way it is. JMHO's about that.
And there is the fact you can
buy a brand new AM/SSB CB radio for about $110. The uniden 980. While It may not show the same power as your Cobra 25, that is unless both are stock then there won't be much difference at all, the uniden 980 has SSB that is dead on frequency out of the box, and is rock solid as far as drift goes. And the audio is clean and clear.
There are techs that can be recommended. Doug's Custom CB, Bell's CB, Key CB, Mike's Radio Repair, and some others. But you might want to call one and see what the cost would be to have what you want done and make your decision based on that. No one can tell you not to do it. If you like the radio that much then a price ilinit may not be in place, otherwise, it would be better to either fix it yourself or to leave it be. JMHO's. Hope this helps. Sonoma gave you a price that is pretty close for most CB shops. That doesn't include shipping either. Again, do as you will as it's your radio. But there are other options too.
Good day and God Bless.