How much to replace a new laser on the Denon 3910?

Why don't you ask Denon?

I don't know what repair services you have available in your area, but if you have a local repair shop don't overlook them. Replacing a laser isn't rocket science. I just had one replaced on a Raysonic for $180. Two dealers quoted over $400 (plus shipping etc) - one wanted $125 just for the part for which I paid $50 thru a local techie.

It's a jungle out there!

Call Denon America and see(pray) if they have them in stock. I have a highly modified Marantz and had the same concerns. I called Marantz America and found that they still had them in stock for around $90. I bought one even though I don't need one right now. I figured for $90, it's peace of mind to have one around.

I don't know that I could install it myself, but at least I know that I have the necessary part. I can always find a tech if I can't install it.

Try here:
http://www.studiosoundelectronics.com/cdlasers.htm
or:
http://www.partstore.com/SearchResults.aspx?q=laser+pickup&mcfilt=3&cfilt=10%2C4%2C11%2C851%2C5%2C711%2C17%2C714%2C18%2C9%2C12%2C13%2C644

All the best,
Nonoise