Will this break my xmarks collection and, after I've added content, can I revert the new stuff back into xmarks later? I have been shepherding my collection sin

Will this break my xmarks collection and, after I've added content, can I revert the new stuff back into xmarks later? I have been shepherding my collection since before del.icio.us had a bookmarklet, indeed since Netscape. Xmarks, despite its warts, at least it has cleanup tools I can us now and again, and I can take it with me to Firefox or Safari if needs be.