Hi everyone.  I am just getting back into bicycling. I rode basic non suspension mountain bikes way back in the day.  I recently found a VGC 1999 K2 OZM with the cross link fork with the smart shock. Everything appears original.

Unfortunately I weigh in at around 260lbs and figure I need the stiffer springs. From what I have read I believe I need to find a NB2-650 for the rear and a NB2L-250 for the front.

Are these available? Is changing them out reasonably simple? Should I be replacing anything else with the shock while I am at it?

Should I ditch the original shocks and go with something different?
I would like to be able to ride the bike both off and on the road. Are there lockout options?

I appreciate any help you can offer!
Cheers

Yes the smart shock still works. Bike had been in a storage unit for some time. Looks like it saw very little use and no abuse.  Everything is original and in good working order. 
Cheers