aepeszel,
It could be a simple task or a complex one, depending on what kind of criteria you have for "adding values". Dimensions always keep the true measurements readily available without the need of further calculation but, as we all know, the dimension text can be overridden with all sorts of values.
If you only want to add true measurements, it's a simple matter of gathering the measurements and do the calculation (and of course distinguishing between angles and lengths). If you want to dig into the dimension texts, you'd probably need to consider tolerances, alternative units, prefixes, suffixes etc.