Call around to some of the junk yards, look for a Ford 8.8, but it has to be out of an explorer, they come with 31 spline shafts. I picked mine up from a u-pull it yard just so I knew for sure it came out of an explorer. I picked it up on the half day special they ran once a year, got it for under $100. Then to gear it, would cost about $600 (cost of gears, install kit and someone to set the gears) plus the cost of a new driveshaft, add about $300, and then the MORE bracket kit for the control arm mounts and trac bar mounts add about another $300. If you know someone who can weld that will save you that cost, so about $1300.
If you call around to some yards they will have them already pulled, and you can get it with the gear ratio you want, 3.73, will run you about $400 (as apposed to the $100 axle, $600 set up being $700), then the MORE kit and drive shaft for a total this way of $1000.
That said, to fix your current axle is going to cost you about the same $600 for the gears and labor to set them, last time I checked I think the carrier is $100, you will need bearings and such, and not sure if when the carrier and gears went if they did damage to the axle shafts so might want to replace those too, another $150 (unless you can find used). So you can for a little more get an 8.8 which will last you the life of the rig, or polish the D35 that will break again.
I would call around and see, I say it will cost you $400, as most of the yards wanted $300-$350 when I called a few years ago, but there were a few that said $250, just be sure to crack the case and count the splines to know for sure it came out of an explorer and has the 31 spline shafts.