1979-1980 Suzuki RM 125 shocks are sealed units. You can change oil and regas 1980 shocks.But you can not replace seals.
As long as your shocks are in good shape, no rusted shafts, good bushes etc, they can be modified to be rebuildable. you will need at least new seal heads to suit your shaft diameter plus some machining to shock bodies to fit new seal heads. It is usualy internal thread(Works Shocks) or internal groove (Ohlins). RAD motorcycle in Qld should be able to help. Or if you can get suitable sealheds, 36mm OD and 12.5mm shaft diameter, than any good machine shop should be able to do all the machining for you.
If your shocks are in good shape it may be worth doing it. If not you are beter of geting YSS, or Works for $600 or Ohlins for $1000
hope it helps.