Juan Manuel Tienda shuttle is the bets option to get between the two airports (if there are 2-3 of you, taxi would be faster/cheaper). There should be a website. Shouldn't cost more than USD 20.

As for Ushia (sp), it's all there in the databases. If you want to try domestic fares, try www.legatours.com (I used them last year, asl for Mariela).