It is best to get the pliers. Even with the right tool it's kind of a P.I.T.A. the first couple of times. You can get it off with a screwdriver but it will probably bend it. Even if you don't bend it gettin it off it's a beeeach to get it back on.
If you gotta do it now, put the blade of a screwdriver in the split and turn the driver and it willspreadthe ringand you can replace the lever. You can ride without the ring for a bit just keep an eye on the pin and push it down if it starts poppin up, and get a new one as soon as you can.
I have done 4 sets of levers and never succeeded in saving the c clips I removed. Last change I changed to e not c clips from automotive supply and WAY easier to install/remove. Take the pin with you and try fit at store. John