. You probably want to change the recoil springs with new Wolff gunsprings depending how old it is and how much it has been fired. Russell
Welcome to the forum.
Russell is correct in that you should evaluate the condition of the springs of your new-to-you P1. But note that there seems to be some debate as to whether swapping out the springs should be mandatory, as many people believe and strongly advocate. Some folks who shoot the P1 (and the P38) a great deal maintain that it is essential to change the springs before your first trip to the range. Others disagree and can see no appreciable advantage or difference in the performance of guns that are updated with new springs and guns that are not.
I recently swapped out the springs on a P1 shooter that I, too, got from Dan's Ammo (great guns, in great condition, at great prices, I might add), even though the local gunsmith who evaluated it said that it was a waste of time and money. My gun dated to 1977, but the condition of the original springs was -- in the smithy's opinion, at least -- perfect. I also couldn't detect any difference in the performance of the gun before or after the swap. (I did it mainly to stop the brass from flying directly into my face or on top of my head, a somewhat common condition with the P1. After a couple of fine-tunings by the smithy, the gun is now ejecting its spent brass back and to the left -- just as advertised.)
Some folks also maintain that you should not under any circumstances get the updated, extra-power recoil springs that Wolf sells for the P1 and the P38; these folks believe that the more-powerful springs cause too much of a slamming action and will crack or otherwise damage the alloy frame and other goodies. Conversely, there seems to be an equal number of folks who believe strongly in the exact opposite opinion. Everyone's an expert, in other words.
If you check out the discussion on P1 shooters on the P38 forum,
http://www.p38forum.com/
you'll get as much as you want on the topic (look in the Post-War P38 section). Good luck.