Luther is definitely not a Calvinist and traditional-style Lutherans will tell you upfront that they are about as far away from Presbyterian Calvinist as from Wesleyan Arminians.
A WELS article is here:
http://www.wels.net/cgi-bin/site.pl?1518&cuTopic_topicID=10&cuItem_itemID=5678
Today's Lutherans are about as far from Luther as today's PCUSA is from Calvin.
More's the pity.
Actually, they are not that far apart, and the only real point of departure (at least in the context of the present conversation) is on the issue of reprobation, not election. They disagree on one aspect of predestination, not the doctrine of predestination as a whole. Lutherans simply stop short on the philosophical and logical examination of the premises to form certain conclusions. They simply choose to embrace a mystery rather than attempt to better understand it. Though I disagree with the conclusion I cannot fault them for the notion.
The attempt here to paint Luther as so minimizing the doctrine of predestination as to make it obscure and peripheral is not reflected in Luther's works:
In this, moreover, I give you great praise, and proclaim it—you alone in pre-eminent distinction from all others, have entered upon the thing itself; that is, the grand turning point of the cause; and, have not wearied me with those irrelevant points about popery, purgatory, indulgences, and other like baubles, rather than causes, with which all have hitherto tried to hunt me down,—though in vain! You, and you alone saw, what was the grand hinge upon which the whole turned, and therefore you attacked the vital part at once; for which, from my heart, I thank you." - The Bondage of the Will (conclusion)As far as Luther's statements that we should not search the hidden things of God, this is nothing new. He said it throughout his life, and Calvin was in full agreement with him. It is certainly not indicative of any change of mind with respect to predestination.