Your nutrients are going to accumulate regardless if all you do is try to replace that skimmer.
I would cut the supply and return pipes, clamp on some flexible hose and set up a rubbermaid tub as a new sump, totally bypassing that existing tiny sump.
Trying to move a tank with nutrient and GHA issues will cause a lot of headaches when you move up to your next larger tank.
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Mitch
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