If you're blowing fuses regularly, then that means you've got a problem. I'd replace the rectifier tube first, and then the power tubes. If that doesn't fix it, then I'd take it to a tech. Or you may want to take it to a tech first. It's possible you may have a problem somewhere that is ruining the tubes, so you could ruin your new tubes switching them out while the amp isn't functioning properly.
I had a similar problem with my DR. Turned out to be a bad rectifier tube, so that's the first place I'd look.