Can anyone help me please! Will the Hitech 645MG or 625MG servo fit directly into the Kyosho Inferno RTR using the standard kyosho/perfex receiver that it comes with? I am just a newb and my stock servos are dead.

Yes it will, although you may experience some problems with the 645mg servo. I would suggest a different servo such as the 625MG. But yes it will work with the stock stuff, although I would reccomend going on ebay, and buying a better radio, such as the Xr3i, and get the one with servos

there are common problems with the 600 series failing i.e the 645 and 625 but some people i know have had them servos in his bug for over a year now with no problems

my 645 an 625 failed[&o] a good servo to buy is the ACE DS1013 very durable no problems with them, waterproof,dustproof 13k of torque and at 10secs one hell of a servo
also another great servo is the sanwa erg-rz

I would suggest going with either a Hitec 925 or 945. I myself have gone through about 7 of each of the 625 and 645. Since switching to the Hitec 900 series servos, I have had no issues with the servos whatsoever.

I always strip the gears in these servos.......They work ok...But I guess I don;t know how to set my servo saver up right or something to loose maybe?

good thing the gear sets sell for 17$ at tower...

Save up money and get a high-end servo that will last you forever, it will really help with the steering of the car. I use a Airtronics 94358Z and ive been very very happy with it.