If I hire and SEO to tell me how my pages should change to rank higher, will he/she actually create those pages and then upload them or do they just make recommendations and then I have to have my web designer make the changes and upload the pages?
no a SEO only optimizes your pages to get higher rank. you have to pay the web designer to make the webpages, then the SEO will add extra coding that will compatibalize your webpage with serach engines in order to rank higher
Actually, there are some SEO companies who will actually do the work on your site that they recommend (and you approve of). And there are other companies who are consultants only -- they'll tell you what improvements are needed, but they won't touch your site. You have to make the changes, or have your webmaster make them.
This is something to ask when interviewing companies about their services.
Typically having a 5 star web designer and a 5 star SEO expert in the same person is like having Michael Jordan and Barry Bonds in the same person. Doesn't happen often (if ever), and most clients don't usually understand that.
If you are working with a great SEO company, they should be able to do both (by using two people working together). What you don't want is for a web designer to build "non seo friendly pages" and have to redo them, and you also don't want your SEO guy to mess up the code, while expanding your site. Hope that helps.