[stevedusa]

Welcome to PPCGeeks.

As your case, do browse the "CDMA Touch Pro Upgrade" section, link to the top of the page.

Since you already have it HardSPL unlocked, yes you can actually flash ROM using the SD card. Do check out the sticky topics in that section and you will be able to obtain the information you need.

As for the ROM? I personlly prefer the Might Mike's ROM. Of course there are other ROMs out there so try them out and see which one fit you the best.

As for the lag in GPS? Well it's a common problem, so far no real fix but deal with it. Keyboard lag? Flash a new ROM and you'll be good.