Take this photo to your local Lowe's or other hardware store. They can advise on the proper technique for both projects and sell you the tiles, paint, etc. The brass looks to be in good condition. Consider selling it on Craig's List and starting with a new set of doors or updated firescreen.

the insert looks so much better black! good choice!

You will need to seal the brick with a masonry sealer, before installing tile over the brick. It isn't hard.
Here are my concerns: 1. have you tiled previously? You say glass tile. Do you mean mosaic? You have deep channels in the brick. You can fill them with the adhesive, but it is really important that mosaic lay completely flat. Larger tiles will span these grooves. The edge of mosaics might dip into those channels if you aren't meticulous. Grouting mosaic is a pain in the butt. 2. When I did this, I removed and replaced the surround/mantle. You don't say that you are planning to do this. Adding a layer of tile will change the depth of the fireplace and change the way you surround looks and how the grate currently fits. You will probably get adhesive and/or grout on the surround. You need to tile into the firebox 3-4", the depth of the brick, in case you ever want to change the screen and go with something else, like a gas fireplace. If you don't, they will discontinue that tile and you won't be able to match it. The inner rim of tile should be done before you do the face of the fireplace so you can cover the raw edge with the face tile. 3. You want to paint the hearth? You might want to rethink this. If you chisel out the hearth you might find that the brick is only 1/2 inch thick decorative facing brick and a regular thickness new matching tile and adhesive will bring it up level with the floor, or you might find a full depth brick, in which case hardi-backer cut to size, plus mortar and a new matching tile can level it out. The hearth tile goes in last.
I have no doubt with enough research, internet videos, a tile saw, plenty of time (don't rush. plan that this might take days or several weekends) and the right tile, and planning, that you can do this yourself.