synaptic is workable with mandriva, but a dependency nightmare. I was using it last year.(apt-get, and more)
It would be best to leave urpmi alone if you have it set up. In case you later require it.
No point throwing away all that data.
The best bet is to do as you suggest, go to an easy-urpmi site (this ones good)
http://www.mandrivauser.de/smarturpmi/
and where you have a choice, select smart instead of urpmi.
You may also select synthesis instead of hdlist.cz,
it's faster because it's smaller(meaning less details about packages)
I got smart, smart-gui, etc from MDE...
http://www.mde.djura.org/