Not sure what material you are using that it got "hardened." Probably good to cultivate a little to break it up (with a "claw" or hoe or ??? depending on space) and then topdress with new mulch. No need to replace; the idea is that the old mulch decomposes into the soil and helps improve the soil’s texture. That’s why I never use large mulch like big bark chips. Always something medium to finer textured and that will degrade; best is something pre-composted (shredded aged leaves, composted stable bedding….).