IN SEPARATE MEDIUM BOWLS, soak the mung bean noodles and tree-ear mushrooms with water until soft and pliable. Drain the noodles and cut into shorter lengths; set aside.
Remove the hard centers from the mushrooms, coarsely chop and set aside. In a medium bowl, combine the pork, garlic, fish sauce and ground pepper. Mix in crab meat, tree-ear mushrooms, carrots, bean sprouts, shallots and bean thread noodles; set aside.
Combine the warm water and sugar in a bowl. Lay 1 rice paper wrapper on a damp towel. (Keep unused wrappers in their package.) Generously brush it with the sugar water; allow it to soften to a very pliable wrapper, about 30 seconds or sometime longer (depending upon the brand).
With your hands shape 3 tablespoons filling into a tight compact 1-inch-wide-by-4-to-5-inch-long cylinder. Place cylinder along the lower edge of wrapper. Roll the bottom up and over the roll tightly.
Fold both outside edges inward to enclose the ends. Continue rolling up into a cylinder; set aside covered with plastic wrap. Repeat until all the rolls are done. To cook and brown evenly, the roll must be firm and evenly packed.
If the wrapper has a tear, bandage it with a softened rice-paper remnant. In a preheated wok or saucepan, add oil to a depth of 2 inches and heat to 325F. Add a few rolls at a time, but do not crowd. Fry for 10 seconds.
Immediately increase to high heat or 375F. Fry, turning occasionally until golden brown, about 6 to 8 minutes. Remove and drain on paper towel.
Cut crosswise into 1+1/2-inch pieces. Arrange rolls on a plate lined with lettuce. On another plate, arrange leaves of lettuce, fresh coriander and mint leaves. To eat, wrap spring-roll garnish with sprig of coriander and mint leaves in a lettuce leaf and dip into nuoc cham sauce