How to switch to REPLACE mode in VIM
Solution 1:
From the ViM manual:
5. Replace mode *Replace* *Replace-mode* *mode-replace* Enter Replace mode with the "R" command in normal mode.
Of course you can map any key to R, for example by doing
:map <F5> R
Solution 2:
You can press R and you'll get into the REPLACE mode.
Solution 3:
R brings you into replace mode.