I admit in advance that I am not an expert in this, but for those responsible, I would suggest a very detailed comparison between the HTML and XHTML. Most important is what is the purpose of moving to XHTML. Moving to this strict format must provide benefits to offset the pain involved in conversion. Essentially any proc/page which returns HTML must be reviewed ... in the context of any valid input. Stylesheets, javascript, all of these are not the same under XHTML.
The easiest suggestion is to look for a dynamic site which actually does what you think you want to do. There may be simple solutions, but best to build upon the work of others. I hope these example sites exist, but don't be the first unless you have an expert.
