Dear Rosemary,

I can't answer all your questions. But I can give you some idea if you can
afford a Yellow HeNe. These prices are from the Edmund Industrial Optics
Catalogue (2000).

"Unipase" He Ne Lasers

Green  HeNe       1.5mW      >20,000hrs lifetime        $1,320 US
Yellow  HeNe       1.0mW     >20,000hrs lifetime        $   950 US
Orange HeNe       3.0mW     >20,000hrs lifetime        $   920 US

So I don't think they'll break the bank.

I cannot personally recommend these lasers as I haven't used them. Nor do I
know enough about lasers to say if they would be perfect for confocal. But
to my ignorant brain they look promising!

I have no association with Edmund Industrial Optics.

Cheers.