When you synchronize[sic] TL2 with your eBay account it will import all your current listings and whatever unsold and sold ones that are in your account (last 60 days?).

So you will lose any prepared listings, but will have everything you currently have on eBay. A start, at least.

Yes, you might as well delete the TL1 files, they are obsolete.

Also, before doing anything in TL2, do a full system update to pick up the updates since the last version of TL2 was written. And check for updates regularly.