My expectations aren't very high. Dallas has had 3 big problems all season -- turnovers (particularly poor play at PG), rebounding and interior defense. Dirk will help a lot with the first one since he can bail out an offense at the end of the shot clock, but those other two will be Achilles heels regardless. At this point, I think the best Mavs fans can hope for is if Dallas can play a competitive first-round series. They might be able to sneak into the second round if they could get into the 3-6 range, but given the hole they are likely to be in when Dirk gets back in a few weeks, that's pretty unrealistic.
I've been on the Brandan Wright bandwagon since last year. He's an athletic 6'10 with a 7'4 wingspan and a soft touch, so he can be pretty unstoppable on the pick-and-roll -- he just jumps over people and scores over the top of the defense. That's how someone shoots 66% from the field. He does have some serious flaws in his game -- his defensive awareness is iffy, his energy level is inconsistent and his rebounding is terrible: he averages 6.5 rebounds per-36 minutes, which is awful for a "big man". That being said, Dallas is 8-3 when he plays more than 17+ minutes a game and is 4-9 when he plays less. I don't think that's a coincidence.
I wrote an article about that over at the Two Man Game -- http://www.thetwomangame.com/
2012/12/lessons-of-youth/-- The Mavs have been making the same mistakes Miami made back in 2011, when they signed a bunch of washed up old guys (Dampier, Arroyo, House etc.) to fill out their bench. Experience is great, but that's only if you can still play: it does no good to know where you need to be on the court if you can't get there in time.
Delonte West is an excellent player, but I can't really blame Dallas for that one since no other team has signed him. There are reasons for that which go beyond basketball. Strictly from an on-court perspective, he'd be useful to pretty much any team in the NBA. He wouldn't look bad in Miami really.
It's a smart move given the limitations of this roster. Marion has been an absolute rock for this team; he's consistently been one of the most underrated players in the NBA since he entered the league. He's a better defender and rebounder than any of the Mavs big men, so you're not losing anything by going small and you're becoming a much faster and better shooting team. If Dallas had a quality PG, he would still be able to give you a nightly double-double at the age of 34. Pretty incredible.
That's a tough question. I'm not as down on the Lakers as everyone else; when you look at how thin their roster is, you have to reserve judgement until all 4 of their stars are healthy. For now, I'd say Oklahoma City is the class of the West followed closely by Memphis at #2 and then San Antonio/Clippers in the 3-4 range. I don't see the Mavs giving either the Thunder or the Grizzlies too much trouble in a seven-game series. For Derek Fisher's sake, let's hope he doesn't have to defend Russell Westbrook in a playoff game.