Shaun, you don't have to on a Glock as the stock spring is sufficient. Glock and others tune their handguns for optimal performance with SAAMI pressure loads and when using +P (increase in pressure, slide velocity), I do recommend a minimal of a +2lb spring to keep things balanced out. Even heavier spring lbs if touching on +P+. Cheers and stay safe!

Ok looked through the threads, Gen4 Glock 21 is going to be fine in a factory configuration, shooting plus P, no change to the recoil spring is necessary. But personally if it were me and if I was planning on running a lot of plus p through a Glock I\'d change the guide rod to a steel one, id use the same weight spring but would feel better having steel for the guide rod over polymere.
Lone wolf makes a stainless steel one for under $25.
In stock here
midwayusa.com/product/1004110587

Not if the pistol is rated for plus P, I don't remember what pistol you said you bought, if I remember correctly it was a Springfield XDM, Or a Glock 21, either of those would be fine with the stock recoil spring as will most modern pistols.