Dand: there are lots of repair and replacement parts available for the P38 from Numrich, AMCO or SARCO. One of them sells a kit with a bunch of stuff in it, including springs. Also though, if you search for Walther P38 parts you will get a tremendous amount of information from sites other than these three and parts seem to be much more readily available, and cheaper.
Current ammo - if by that you mean +P or +P+. the answer is NO. The Luger P08, the Walther P38 and the Mauser C96 in 9mm were all designed to run on 124/5 gn ball ammo at 1100'/sec or a hair less, period. I like my Walther but I like my hands, face and eyes even more. Fourty yeras ago when those pistols were only 20 years old it was ok to run some hot reloads through them but now that those same pistols are nearing 70 years old I would opt for original mil-spec ammo, which was hot enough to knock GIs off their feet during WWII.
As for accuracy - most of them would shoot 3-4" at 25m but you can easily do better with practice. Every dogone time I take pm P38 out I have to refamiliarize myself with the trigger before I can put them into the bull. One thing any P38 could really use is a trigger stop like we have on target 1911 triggers, it would sure take up a whole bunch of overtravel after let-off.