Help on Winhex

I'm trying to edit this:
1708,6,8,20,6,2000,2000,1200,1000,0,0,0,50,2,0,4,2 ,0,0,0,0,0,0,10,5,0,2,12,5,

to:
1708,6,8,20,6,2000,2000,1200,500,0,0,0,50,20,0,4,2,0,0,0,0,0,0,10,5,0,2,12,5,

how do i get rid of the '0' in the 1000 and add a '0' to the 2? it overwrites the comma next to the 2 and doesnt let me delete the 0 in 1000, help please

For the '1000' to '500'
--click on one of the zeroes in the '1000' to where the cursor is blinking on it.
--while holding down the shift key, press the left arrow button, then the right arrow button
--that will ensure you have the zero highlighted that you clicked on
--press delete key
--change the now '100' to '500' by simply overwriting the 1 with a 5

For the '2' to '20'
--click the number two
--press the 'insert' key which is just left of the 'Home' key. It will ask you how many to add, put in a '1' and hit enter.
--then, overwrite the '2 ' with '20'