i would just go down to radio shack and get a replacement resistor.
make sure you are working on a E.S.D. safe mat.
i am assuming you know how to avoid being shocked with high voltage....
clip the old one out with wire cutters..
with the soldering iron, heat up the wire and pull them out of the board, solder wick out the solder in the holes, you may need to add solder flux on the solder wick to get it all out...
if you don't know anything about soldering than read up and get some practice on perf board first..... that is a nice amp to learn on...
bend the new resistor
install it on the board
use rosin core solder and solder it in from the non component side, clip the excessive wire length
clean up that board with some isopropyl alcohol and q tips....
i hate it when i see so much flux on a board like yours... the excessive flux will with time eat away at stuff...
you may find a local guitar geek/electronic tech that could give you a hand in the repair...
peace minatour87
Rest in peace DIME.