Not sure exactly what you are asking here.

Increasing the number of teeth in the chainring is the same as decreasing the number of teeth in the cog...both will make it harder to pedal. You can calculate the effects of adding or subtracting teeth to either than chainring or cog by calculating the gear ratio (chainring teeth/cog teeth). The higher the ratio, the harder it is to pedal.

Replacing the chainring is easy...it involves loosening and tightening 4-5 allen bolts.