I replaced just the seals on mine. Put it all back together and filled it up with fluids.

Still leaked - had to replace the pump and do it all over.

I would for sure plan on replacing everything.

The mechanical seals in the LTs are not usually the reason for the water pumps leaking out of the weep hole.   90% of the time the impellor has compressed and the shaft is protruding above the surface that the rubber faced washer is suppose to seal on.  Replace the impellor or grind the end of the shaft so that it is a few thousands below the sealing surface