I think its likely israel will comply. The order is pretty weak and mostly stuff israel already claims to be doing. It wouldn't be worth the PR hassle to ignore it.
Even if doing what the ICJ wants is easy, there's a strong reason not to (from their perspective) - it implies the ICJ should be obeyed and legitimizes them. But why should Israel do that? It's just another leftie NGO from Netenyahu's perspective. Start following what those guys want and soon they will have to do nothing even as Hamas attacks again and again.
Considering how reliant Netenyahu's political career was/is on Hamas continuing to exist it's likely that's going to happen anyway. An actual long-term solution would be a huge blow to all of the right.
If israel wanted to deligetimize the ICJ they wouldn't have participated in the case in the first place. Now that they have sent lawyers, appointed an ad hoc judge, its too late tobpretend they think it is illigetiment.