3 questions re: Rega RB 600/RB 1000

Hi
I have several questions regarding RB 600/RB 1000 tonearms.
I would appreciate your help in answering them.
1. I have RB 600 tonearm that i just mounted on Michell Gyro SE.The tonearm was used for 7 or 8 years on P25 table with dialed weight 1,7g.The slider under the tonearm (is it anti-skating?)with 0,1 &2 positions was on 0 all these years.Could it somehow messed up the tonearm bearings?

2.Towards Christmas i will have around 2k to burn on upgrades.Should i go for RB 1000 arm or should i just keep RB 600 and put 2k towards a better cartridge.Right now i have 3 cartridges,all of them are under 1k:Dynavector 10x4,Shelter 501 and Sumiko Blackbird.
Which upgrade will be better:rb 600 with new $2000 cartridge or rb 1000 with my existing ones?
3.Does RB 1000 has the same wiring as rb600?Does it have the same cheap Neutrik connectors ?How big is the step up torb 1000 sounwise?Thank You very much.