Do you mean the APL upgrade?
Check out audiocircles.com. API had a forum there. Alex is a highly repected modder. There are several modders who all seem to have excellent mods. Check them all out. I do see a new mod on the 3910 on reference audio mods here on audiogon. Check there too. Get all your questions answered and then pick your modder. Good luck and let us know how you do. The 3910 appears to take well to these mods....cheers
Go to www.referenceaudiomods.com and click on the Denon DVD-2900/3910 section.
Prices vary greatly according to what you have done.
Looks like their ALL OUT MODDED DVD-3910 is $3455.00 including a brand new unit, and $2455.00 if YOU supply the unit to be modded.
I may sell my Linn and go this route, or purchase a used Esoteric DV-50 and have it super modded by Reference Audio Mods. After hearing a modded Toshiba SD-4960 with less than 1 K TOTAL in the machine and all the mods basically match my Linn Unidisc, they must be doing something right!
I AM IN NO WAY AFFILILIATED WITH REFERENCE AUDIO MODS OR ITS OWNERS.