Make sure the clicker on the tension knob works smoothly, oil or grease.
Drags are not all that tough to work on. Remove the tension knob, retainer spring clip and washer cover. All of the drag washers should come out as 1 piece where all of the washers can then be separated. Pay special attention to the order and clean and lightly grease the entire assembly. Be careful with the non metal washers as they can break. Check your schematic to see if any parts are missing or not in the right order. There are usually 4 metal washers and 3 other felt or other material washers sandwiched alternately (might be 3 + 2). 1 or 2 of the metal washers are usually notched or keyed and only fit in 1 way.
I replaced the felt washers with carbon fiber washers I found on Ebay. Not real cheap in comparison to felt, but work nicely.