Oswalt + their top prospect and/or a good reliever would be about right as a starting point for such a trade. Also, Houston wouldn't do it because their 1B - though aging - is a decent player whose numbers haven't fallen off the post-prime cliff yet.
Trading Kubel would be easier than trading Cuddyer (due to much lower salary). However, we wouldn't likely see much coming to MN in exchange for him given his mediocre season thus far. If he has a really good couple weeks, his value might go up enough to generate some interest, but I doubt it.
Interesting stat shown before the game tonight:
Twins runs per game prior to their slump starting in early June: 4.7
Twins runs per game after slump commenced: 4.6
As I've said - offense isn't the problem. Their ERA jumped a full run per game. I think the bullpen would be ok if they improved their starting rotation - that part of the pitching staff was doing well for a couple months before the starters fell apart over the past 6 weeks.