The stock 45 Frame is plastic and -MAY- crack during play. I used my stock frame for quite awhile with no problems. *Shrugs.*
I will agree with getting a 45 frame, though. You can achieve a better pull... and the frames simply feel better, in my opinion.
I disagree with replacing the 3-way... the stock 3-way and Ram are -excellent- on the 2k's and above. Maybe replace the Pneumatic Reg down the road to an adjustable one... but you really don't need to. The more you leave alone the more likely you'll have a working gun at the end of the day.