By the time I post this I'm going to hazard the guess that yes, there's an easier way. For the moment this is how I'm re-formatting the old GR reviews that are now a block of unreadable text.
I could go back and re-edit them all, one by one - but that's tedious, plus I quickly got tired of having to save then be kicked back to the default Dashboard page. (Or Blog page). Also for now I just want to tidy up those old reviews I want to link/refer to.
1) Search for the book you reviewed - choose the "bookshelf" option in the pull down to search your own shelves.
2) Note the url of that review webpage:
Example: http://batgrl.booklikes.com/post/XXXXX/post - the Xs will be numbers
3) Now change that url to:
Example: http://booklikes.com/post/text/XXXXX - use the same number as the review page
Note that your user name is no longer in the url, it's now just booklikes.com - and there's an additional word text in there. That url should send you to the edit page for that book review entry.
That's how I'm managing it at the moment. (I suspect Booklikes will eventually make this easier.) Let me know if you have a faster/easier way!