That was exactly our situation. I am not beyond ignorant when it comes with electrical work. I can change or add new circuits or run them off existing lines. But when I called our electrician to come and install our GFCI panel outside I certainly felt like one.
He took one look at the main panel (200amp) and told me ''no problem you got plenty of capacity here''
I said ''but all the slots are taken and by my count I end up at 210amps''
''I could start a fire if everything was on'':o His response a very long drawn out chuckle that was filled with confidence.
He proceeded to explain exactly what Brewman and UTS are describing here. In the end, no major work just simply some reworking of breakers, the installation of the GFCI panel, some wire and a solid lesson learned by yours truly, Don't mess with that doodoo unless you are qualified to mess with.
ps. the moderator may feel like this is too riské and is more than welcome to edit.