If you only wear them for black tie, it's unlikely they will ever crease much--but then, your lifestyle might be a lot fancier than mine. As for maintenance, Saphir sells a liquid cleaner/polish specifically for patent leather. It's what I use. Seems to work quite well at getting out scuffs and scratches.
Honestly, I'd stay away from opera pumps. Unless you're always impeccably dressed, opera pumps will look really bad, IMO IMO IMO. I just think in this day and ago opera pumps look too feminine for most people. Everyone will be asking why you're wearing women's shoes.
Brooks Brothers sells the entry level patent leather shoes, made by Church I think. I own a pair. They're fine although I'm not a fan of the last.