Usually to remove riverts, you drill through them with the same size drill bit, or at worst, chop the headfs off with a sharp chisel (I use a carpenters chisel bc I have a few).
I had replace a window mechanism and window and drilled out the riverts then replaced the riverts with some 3/16" stainless bolts and nuts (only cause it looked easier and I had them, and I had no long 3/16" riverts )
Replacing the lock is not all that hard but fiddly, and I think I used side cutters to move the U shaped clip holding the lock.
Have not done one in a number of years so really cannot remember.
If you are right handed, drivers side door internals are fiddly where as passanger side are usually easier.
Of course if you are left handed then the reverse applies.
I remember removing the door pins in a door and cut a slot in a cold chisel to use to start the pins moving.
I used the 100mm/4" angle grinder to cut the piece out of the chisel but I am sure I have seen specific tools for the job on ebay..
Before you start I suggest vacuuming the bottom of the door to remove any dirt bc you will most likely drop something.
Then vac again when completed to remove any drilling swarf.
I have a couple of small magnets for retrieval of said dropped items.
Of course if in doubt I pull the oxy torch out.