how do I know if I uninstalled something I shouldn't have
First of all, if you are not 100% sure which system apps you can uninstall, it is better to freeze them first (which is supported by e.g. Titanium Backup and other apps). So if something starts behaving weird, you can simply unfreeze those apps again.

As you probably haven't just frozen the resp. apps, let's move to the second option: You hopefully made a Nandroid Backup before starting to tamper with the system? In that case, you can restore this backup via ClockworkMod. Or if you at least backed-up those apps you uninstalled (e.g. with aforementioned Titanium Backup), you can use this to restore them again.

If this is no option neither, all what remains is to check for a fresh firmware image to flash -- either stock or custom ROM.