Go to vinylengine.com and get all the info about Rega tweaking.
I had a P5 years ago and found the subplatter and belt the best bang for the buck upgrade. I did find speed noticeably faster(even with the optional power supply)which was one of the things that wore me down to invest in a more substantial table.
Hindsight, all the other mods I did where a waste of money if you are more than a casual listener.
All the Rega tables are great for what they are and the upgrade thing becomes a slippery slope after addressing the subplatter issue IMO. You may find-wow, if the subplatter made such a difference, what if I change the...???$$$$
Since you got the table for cheap, investing a few bucks may be worthwhile. I would leave the glass platter alone, as it contributes to the Rega "sound" and look for a real cork mat and maybe replace the rubber band suspended motor with the upgrade as well.
Another consideration, invest as much as you can in a phono stage to hear what the the table is capable of if you don't already have a decent one. Happy listening!