I'll agree, if this is from a Mossberg, I wouldnt spend much money on it, or consider doing it myself.
Cold bluing isnt all that difficult, most of the work is done in the prep stage. You'll need an acid bath to help take off the old bluing, along with sandpaper and steel wool. Get it cleaned and sanded down to 400 grit.
The bluing part is simple. Wipe the bluing agent onto the barrel as evenly as possible, then hang it in a humid area. After the required hanging time, it gets drenched in boiling distilled water; rub down lightly with steel wool and repeat until you have the desired look on the barrel(I usually blue 5 times). After the last time, wipe down with Rem-Oil. Plan on using at least half a bottle as it will be absorbed.