Vintage Dual 1228 Turntable : worth to upgrade cartridge ?


I have from my college days (1977) Dual 1228 with original fitted Shure M95ED cartridge .  It is maintained well , not used for about 20 years in between , but just cleaned , lubricated , resoldered some loose connections , etc and just runs great for me. 
I am not too much into analogue , so not planning to do big time investment into new TT , Phono preamp , but if  can get larger benefit by replacing the Shure M 95 ED with some new cart upto $ 200-300 , I would like to do it . 
My Phono preamp is very low end Cambridge Audio MM 551P . To go with new upgraded cartridge , I may even consider to buy used Phono with budget of $1000 . 
I would appreciate advice form FMs here , where I should spend my money to get most benifit on sound improvement . New cart , new phono ? 

radni
Post removed 
Thanks for your responses . The verdict is quite clear about old Dual 1228. I will not do for upgrade of cartridge as not worth it. 
I will consider again if I am wanting to go into this serious business of Analog , and if I decide to go I will put a starting budget of $3000 for a new TT and cartridge , and further $500-1000 down the road for a used phono preamp . But I have to first make up my mind if  its my cup of tea. 
Thank you , ebm, orpheus10 and tooblue . 

Yogiboy,
will Shure M97XE be a good upgrade over my current Shure M95ED ?  M97XE is only $100 , so I don't mind buying it even if there is noticeable improvement . Will M97XE fit on my Dual 1228 arm ? 
Thanks 

radni,
I think the newer M97XE  will be an improvement over the older M95. Yes it will fit the Dual arm. What have you got to lose for  a mere $100 ?