I haven't used Sig's custom shop, but the P239 I just bought has both features mentioned.
The Sig night sights are nice - I can't compare them to standard, because I haven't used them. Most folks assume there's a high liklihood that a defensive shooting will occur in low light, but many also say you won't have time to line up your sights in such a situation. I would probably put night sights on mine if it hadn't come with them.
The SRT trigger is cool, but I doubt I would send mine in for custom work if it didn't have it. Basically on follow up SA shots, you only need to allow the trigger to go a very short distance forward before you can pull again. If you were really trying to rapid fire (maybe IDPA?), I guess it would help. As I said, I'm glad mine has it, but I probably let off far enough between shots that the regular trigger would reset anyway, so I don't know if it's doing anything for me.
Many new gun owners go way, way overboard on the oiling and lubrication
I had to send mine back to Sig for a feed ramp polish, and it came back with gobs of grease everywhere. Don't know if it was just a sloppy job, but I was surprised.
The feed ramp polish job took mine from not feeding hollowpoints to feeding them perfectly, so it definitely can help, but if you have run a bunch of ammo through without issues, I would not want anyone reshaping the ramp at all!
Good luck with your new gun. I absolutely love my P239.
Best,
FT
[EDIT - just noticed you got the DAK, I don't think you can have SRT & DAK. The SRT is for SA follow up shots, all your shots are double action with DAK]