I built my first unassembled slash kit with those and then used those tools for a year. Finally got rid of them since they rounded off all the hex heads 🤣
I really can't say for certain how much would need to be changed, but here is a video that converts a Rustler to a Slash ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-vP6dgv8Na6M.htmlsi=bapzFWWwWC3vetkN
Yep. The grease can be really thick and add friction. Some people like to add diff fluid to the diff only and light oil to the gears. The diff oil can help tighten up the diff and change the handling.