Dral:
The sum of the breaker values is not relevant to what you are trying to determine. Each breaker on each circuit is there to trip in case of a fault in the circuit operation prior to (hopefully) something causing damage. The breaker value has a limiting relationship to the maximum load that CAN be placed on the circuit, but does nothing to tell the OPERATING load you actually are placing on the circuit.
The rating on the service panel is directly related to the OPERATING load.
In terms of knowing whether or not your service panel's load rating is adequate for the loads you are placing on it, you need to do a load calculation. The below link will take you to a page where you can find much more information and a calculation form that may be helpful. Go to the bottom of the page.
http://www.absak.com/design/load.html
In general terms, what you are doing is adding the sum of energy consumption in WATTS:
1: sq ft of the home x some value (often 3) = x watts
2: adding up all of the appliance and significant use circuits: circuit watts + circuit watts + circuit watts
3: totalling the above, and doing some math to average the above use
4: adding in some conditional use appliances
5: totaling your work and dividing by 240v = xxx amps
6: your service panel rating needs to be larger than #5,
hopefully by a comfortable margin, generally considered to be at least a minimum of 10%.
If in doubt, buy a basic manual that has a detailed explanation of the calculations. They are not rocket science, and the manuals are not expensive. These are, however, IMPORTANT calculations. You want to be sure you are operating in a position of comfortable reserves for the sake of safety. Always know and obey local codes, or hire someone to advise you who does.
It is always a good idea to hire a professional electrician when you are working in an area of inexperience. But, and this is a big but, do your homework first so that you know what it is that you are trying to accomplish. If you give him a detailed list, in heirarchic order, of your desires, it is much easier for him to see the whole picture and advise you accordingly. If you educate him fast by doing the homework first, the clock does not run on his meter for anywhere near as long.
