Hello,
Personally I would go with the upgrade option since you want to keep everything as is (content, pages, tracking codes, SEO etc). Every other solution seems more bothersome (to me at least).
I would backup the existing site, upload it in a local server, remove the skin that you know will cause issues, upgrade DNN and modules (keep in mind that it is wise to keep a backup before and after every successful upgrade so that you can do a rollback if something goes wrong). Then I would go to each page and adjust everything that needs adjustment. Replace the current site with the new one and you are done.
From experience I will tell you this: if the upgrades go well and you don't stumble on any major issues, the rest is easy. I had a website running DNN5 and at some point upgraded it to DNN6 (this was upgrade and redesign but since the website had a lot of traffic and had an eshop as well, I had to go with upgrade and not a new installation). Recently we upgraded from DNN6 to DNN8 (this was upgrade without redesign, kept the content as it was), so this is much like your case.

Thank you both for your responses. 

Do you know when 9.1.0 will be released? Also, if I cannot wait for 9.1.0, what version of 8 should I upgrade to?

Sue B.