It has been recommended, here, that you first loosen the fill plug before draining the gear oil, just in case you can't get the fill plug out.
Also, I found that you can't get to the bottom of the trans. case, to clean the magnet, from the passenger side PTO cover. You have much better access from the drivers side cover.
While you are under the truck, you may want to consider adding a "Manual Transmission Filter" from Geno's Garage. About $30. 00 with one filter & $40. 00 with a spare filter and gaskets. Not a bad price.
I bought mine from Quad 4X4 (TDR advertiser) & it came with the spare filter & gaskets and a VCR tape showing you how to do the job. Delivered price was around $61. 00. I'd never done one of these, before, and I thought the tape might be beneficial. Actually, the job is so simple, the extra cost for the tape really isn't necessary. BTW, the filter housing allows for an additional 8 oz. of fluid.
Joe F. (Buffalo)