...Now I got to go clean those dead spiders and caked on dust off the glass in the negative holder. Actually I'm hoping the glass is removable but it does look fixed...
Yes, the glass is removable. Both parts (upper/lower) of the carrier have a plate in natural metal finish, which is held in place with two small screws. If you remove them, then you can remove the plate and so you can remove the glass. So, you can replace the glasses with any insert, or spare glass if yours is damaged. Keep in mind that the upper glass is anti newton ring glass, so cleaning it is probably difficult.
Two more interesting bits about the carrier:
1) The lower half has two "pins" that slide forward - backwards (toward the hinges). When they're in the fully forward position, they're set for 135 film, so you only need to put the film strip against the pins and move it left/right to align the frame to the mask. Likewise, when the pins are at the "backwards" position (close to the hinges), they're set for 120 film. If you have misplaced the negative in the carrier, you don't need to take it off the enlarger. Just lift the front handle of the carrier until it clicks and it will stay there. Realign the film strip, then gently push the silver lever at the handle, which releases the upper part of the carrier and puts it back in contact with the lower half.
2) There's a focussing aid at the lower half of the carrier. Turn the enlarger on with the carrier in place and start pulling it. At some point (about half out), it you'll see two lines projected on the easel. Use the focusing knob until the lines are aligned and so you have focused the enlarger, but this only works with a glass carrier. I've tried it with my glassless carrier, but it doesn't work.