If you open a raw file in the ACR version of Elements, there is no healing tool.
So, as already explained, you can choose to continue the editing in 8 or 16 bits in the editor.
However, as also explained, in the editor in 16 bits you can practically use all global edits and filters, but NO detail tool like the healing brush or layers. So you'll have to convert to 8 bits before using the healing brush tool.
And that is excellent, since 16 bits are totally useless with that tool. They are also useless for layer work so long as you don't play with exotic blend modes; for instance compositing with mask with many layers in normal blend mode is perfectly ok with 8 bits.
Remember that you should mainly beware of posterization; that's where 16 bits are required. Sometimes, that is not enough and you have to add noise to counteract the posterization.