Excel 64 Bit and Legacy VBA - Do I need a complete Re-Write of the Legacy Code?

I had to rebuild my PC at work a few weeks ago and I am on Office 365 E3 and I installed office from the Office 365 portal.

When I went to edit some code in one of our many VBA projects, I got this message:

I've always understood that I'd run into some VBA/Macro issued between 32 and 64 bit office.

My question is do I need to just update the statements as stated in the error message or so I need to plan on complete re-writes of the VBA code in the projects?

Here is where the code fails.

DeclareFunctionDoPDFLib"DOMINOPDF.DLL"(ByValszInputAsString,ByValszOutputAsString,ByValszOptionsAsString)AsLongSubCDO_Mail_Small_Text(rngeSendAsRange,strEmailAsString)DimiMsgAsObjectDimiConfAsObjectDimstrbodyAsStringDimsURLAsString,sPDFAsStringDimoFSObjAsObject,oFSTextStreamAsObjectDimstrHTMLBody...