Alright APUGers -- I am a rookie at this, so please pardon my ignorance.

I recently purchased a DII at a garage sale -- it came with a lense already on it (50mm Nikkon) on a black lense board. It also came with 2 other lenses -- a Besler 75 mm and another 50mm. The current set up seems to work great with my 35mm negs. I would like to print some 6x6 negs, but the current set up leaves the corners rounded and soft. I would like to put in the 75 mm besler to prevent this.

I took out the lense board and examined the board holding the 50mm lense. It looks like the 50mm lense has been securely glued into this board and it would be quite a chore to get it out. I am guessing that the 75 mm besler will not likely fit anyways. Here are my q's:

1. What exactly do I need to get this 75 mm Besler up and going on this enlarger? All I have is the lense.

2. When looking through the Besler lense, it is pretty crappy. A lot of dust on it, spots, etc. I don't see any scratces and I don't think there is any fungus on it. Will the spots on this lense affect my prints? What is the best way to clean this puppy?

3. Also, I am confused about condensors. Looking at my enlarger, I have a bulb in the lamp house, next comes a silver bucket type piece with a lense at the bottom which the light passes through. This is the condensor, right? Next comes the slot of the negs., then the billows, then the lense. Help me if I am mistaken about what I think is the condensor. If this silver bucket like thing isn't the condensor, will I need to get one with a 75mm lense to do 6x6 work?

Any thoughts would be greatly appreciated. Thanks.