You can check out modwright.com for some info on his pricing for other players. That should give you an idea. As far as opening the sound goes, that will probably depend on the mods done and the parts used.
From my experience with modded amps and preamps, bass improves (deeper, stronger) mids and treble are smoother, more extended...everything is much more transparent and lifelike...less "electronic" sounding. Dynamics can improve and noise floor can be lowered too. It likely won't sound like your old player anymore, but I mean that in a good way...you won't mind.
My DAC was built by EVS (tweakaudio.com), so it is came with all of the mod-type parts and tweaking. My transport is a Sony CDP modded by EVS to be a transport and it is amazing (especially considering the cost was $650-ish, including mods). My preamp is a Counterpoint SA5000 (modded by Mile Elliott at Alta Vista) and my amp is a Counterpoint SA100 (rebuilt to a NP100 by Mike Elliott).