What tomearm ?

I don't think a Rega arm will work on that turntable without surgery. Different mount and different pivot-to-spindle distance and effective length.

If there is a problem with your current arm, then just get a replacement Project arm. If you want a better arm, you will need to start with a better turntable.

If the OP cannot reassemble the arm or re-solder the wires I don't really  see how he is going to drill new holes in his plinth to install a Rega arm.  And that's assuming he wanted to in the first place. The Rega is not a drop in replacement, and as I said in my first response, the turntable would need surgery to accommodate it. It's not worth it and would look terrible, even if it could be done.

Sending the arm to a technician to reassemble is the most sensible option.