I'm glad to hear that!
Since Phex still has code to handle the /get/ style requests (as it seems others have, too), I think it wasn't completely replaced, but it is completely obsolete, as requesting by sha1 is the only way to be sure that you get the right file. Since you likely will want to implement the DownloadMesh and Partial Filesharing, you'll need to use that anyway
What you definitely need is a correct Vendor String. Without that you'll get disconnected quickly.
Good luck with your client!
(btw: can I find it somewhere? and is it free software?)