Easiest way to update modified engine?

Hi,
I just downloaded the latests head and surprise... it's very different from the last tag which my work is based on.
But since my version of the engine does not have the CVS folders mergin files doesn't seem to be too easy.

One way I can think of is first checking out copy of the head then simply copying my own files and overwriting the newer files... and then checking out again and start comparing files with diff.

Any other suggestions?


Thanks.