If you want to change a word with a previously yanked word, there's another solution to viwp (once you have yanked the first word).

ciw removes the previous word and puts you in insert mode where it was. But then you can use ctrl+r, 0 to insert the contents of register 0 (which contain the previously yanked word).

So:

yiw
[move to next word]
ciw
ctrl+r
0

recording macros
press q followed by register a-z, q to stop recording
then @a-z to replay,
repeating @@

search for yanked word
yw - puts into default register "
/ -search mode
Ctrl+R- take from register
" - paste content of register "