Well, this will require considerable Dick Tracy talent, given the unknowns.
Before you call in an electrician, see if you can narrow some things down.
First, just in general, you should always know exactly which circuit breaker controls what. This is a good time and a good excuse to get that done. With a helper, go around to every light switch, every recepacle, using a little tester, every appliance. Verify and mark the breaker panel. I actually have little number dots which I put on each switch and receptacle identifying the breaker number.
Anyway. If you have not already figured it out, this will now reveal which switches and receptacles are fed by the tripped breaker. ( Leave it tripped while you are checking everything else.)
NOW, unplug anything plugged into the tripped circuit, and turn off all the switches. Now it is time for the electrician, if you are not comfortable or knowledgeale about working inside the panel. I would put a clamp on ammeter around the wire from the tripped breaker, and turn it on. There should of course be zero at this time. Turn things on and plug things in to see what the current goes up to. If there was a bad "something" like a toaster with a shorted cord, it will now show up.
If this testing fails to reveal a problem, the next step might be to replace the breaker. They can get "weak" or marginal, so just do it.
Given your description of the property and the electrical work, I would remain alert to problems. I might even recommend replacing the breaker in question with an arc-fault model. This way, if there is a marginal or intermittent wire problem, such as from the moust or a nail through the plaster, the AFCI should prevent a fire.
If you are not very comfortable with this, I would definitely recommend getting an electrician, who has more sophisticated test equipment to locate a faulty cable, etc. But as I said, if you do some of the "narrowing down" first, you will not be paying him by the hour for that simple task.