Replacing top rim?

[Dash]

The top black plastic rim of my tank is bugging me. The two front corners have split from the salt buildup. This is a secondhand tank so the cracks were there already to start with. I have salt water seeping over and dripping (very slowly but eventually leaving a salt trail) down the outside of the tank. I guess because the rim is not fully sealed anymore and the water seeps under the plastic and over the top glass rim.

Not the greatest pic, sorry


One side of the plastic rim comes right off if I lift it. My question is, is it possible to get a new plastic rim? Is this commonly done and easy?
Please don't tell me my tank is toast, in which case just lie to me