XXX may be a good opportunity, but you need to find out from them:
1.what exactly they want you to do as pre-sales engineer (such as gathering user requirement, architectural design, a rapid prototype and high-level solution)
2.the solution from the pre-sales is more based on marketing strategy or customer needs
3.how soon usually it is required to provide a preliminary solution?
4.what is the current project will be like?
5.Is this position a new opening or a replacement?