It is hard to describe a sound, but all solid lifter will have some amount of a 'click' when they start to lift. It shouldn't be too much of a rattle, but they will never be as quite as hydraulic lifters. I guess the best thing would be if you could hear a proper running 2.8 and compare.
Adjusting them isn't too big a deal; and a new set of valve cover gasket may slow down any oil leaks. I always adjust mine a little on the tight side, meaning less clearance; just remember that too little clearance won't allow the valves to close all the way when they are hot.
