Trykker is a beautiful serif font, and I can see why you'd like to use it.
In general, eBays and users and people browsing just want the information that they want, loading as quickly as possible. Especially when it comes to eBay listings, the "keep it simple" principle is well worth keeping in mind.
From reading eBay's JavaScript policy, it does seem possible that calling an external stylesheet within a listing will fail. (It was permitted previously, but I rather suspect it's now been disallowed.)
