Will it affect SERP if website content changes?

Let's say I build lots of lots of backlinks to my site (an autoblog).

Then one day, I change the site to an ACTUAL website (no more autoblog). Will this harm SERP?

of course, the SERPs are related to content on website and crawlers check regularly if the content has changed to rectify its position on SERP, so you are regularly monitored for content.

Just think about the ramifications of changing your content site wide...keyword densities and all those other factors gets totally flipped flopped and rearranged. Expect a big google dance in your neighborhood, if it is an autoblog and I assume its wordpress, create a "page" for your homepage, then make that the static page in your settings -> reading panel. Then make another page for your "posts" to still remain. Make a subtle appearing link from the new homepage to your posts page and I think that would work. Content still remains intact and accessible by the spiders.

yes if content changes then your ranking may change as well.