First of all congratulations on your purchase..The P6 is a marvelous handgun for the price..I got mine few months ago, and I went thru the same delemma you are going thru..Shall I change the springs, Shall I refinish the gun, Shall I install night sights..
Well here what i did:
1) you can purchase the springs and change them yourself if you want to..A set of springs is around $20..At least it is worth to buy one set and keep it stored until you see the need to replace the springs..That's what i did.
2) I replace the sights with night sights (around $85)..I took this decision after I fired my P6 for more than 600 rounds and I fell in love with its accuracy and ease of control. Also mine was shooting Hollw points with no issue of whatsoever..So it passed th etest to be qualified for a home defense piece and it deserved the night sights.
3) As for refinishing the gun..I thought and thought and then came to the conclusion that I really like it with the minor holster wear towards the front side of the frame..it just add character to the gun that it is a gun with a history...So I decided to keep it as is. May be one day i'll go with a wooden grip and a refinish coat but the price of ammo has put a hole in my pocket..And I love to shoot more than look at my guns
Shoot the P6 and you will fall in love with it..It is just another fully pledged SIG..with half the price