Am I in for a shock?

Mine is an 04 Corsa sxi with 48k on clock from new. Only previous fault in almost 6 yrs (touch wood) was the replacement of the gear linkage with a new kit (my son had same prob - common fault). However, I have noticed in the last 6 months that the front end/steering is very noisy on uneven roads. Had my front wheels off recently and noticed maybe tell-tale signs of adjacent moisture/oil? on rods etc plus shocks. Pardon my ignorance but does that mean I prob need to have the shocks replaced or can they be filled and resealed. Springs on both sides seem in good shape. If it is the shocks are they an expensive job to fix/replace. Be glad of your help and thanks.........