Hi Myrna
In regards to v3, thats looking like its out in a couple of months from now, autocomplete will likely be included 🙂
In regards to number of fields, this really depends on your server setup what you can get away with.
I have tested S&F with 3k posts, and about 5-10 fields on a shared hosting setup and looks like its running smoothly, however, I’ve heard the occasional user not be able to get away with this.
More fields does as you imply, add more overhead to the plugin, but only really when the fields are dynamic (change based on the selections in other fields), this option can be disabled though if required – and it looks like your existing search is not using this kind of functionality, so if doing a “like for like” it should be possible in my opinion.
I hope that helps, let us know if you have any further questions.
** Just to note, we are on a national holiday in the UK, so replies / support will slower/delayed until we are back on Tuesday.
Thanks