For anyone who has used the Find and Replace function in another program before, you'll know where I'm going with this.

In the edit menu, there would 2 new options called Find, and Replace.

Find will bring up a little window which will allow you to drag any block/reporter/boolean into the search field.
There would then be two radio buttons, one that says “Search this Sprite only”, and “Search all Sprites”. They're self-explanatory.
There would also be a checkbox that says “Check the Block's Parameters” which will make it so the block has to match your search term's block fields.
After you click the Search button, it'll find what you put in the search field. If it finds something, it'll highlight the block and ask you if you want to see the results. If you select Yes, then it'll allow you to cycle through the results until you click cancel.

Replace is just like Find, except it'll ask you for another block to replace your Find term with.

Sorry if that didn't make much sense; I'm tired.