Hi Stu. I think Peter has the correct answer here. If you do not have the Decimator plug-in within Daz the best option is to try exporting as .obj using these settings which will ensure your textures will be OK.
Once exported use Meshlab prior to importing (opening) in Exchange. Peter suggests: (Meshlab: Filters / Remeshing / Quadratic Edge Collapse Decimation (with Textures). and thats what I also used prior to getting the Daz Decimation plug in. If exchange still hangs, then yes, poly's are too high (most likely), or you need more RAM. The only other choice is to export your model from Daz in sections if possible, go through Exchange, export to iClone and reassemble. Thats the best I can do I'm afraid. Hopefully someone else has the ultimate solution. Cheers.