Garry, yes the phono boards can be changed; NA322 MM, NA323 (S, K, or E/R) MC, NA326 Line, or NA328 "CD" boards can be used.
If you are looking for replacement boards, note that they are no longer available to buy new, however Naim dealers often take them in stock secondhand or have pairs of boards tucked away in drawers, so well worth having a ring round some dealers. Otherwise, they are regularly available privately via the usual places online - however caveat emptor applies. Try to find the latest type boards you can, so for MC boards that would be 323/5 and for MM, 322/4.
As for the do and don'ts, just be careful when you slide open the tray from the cover that you don't damage the fascia. Ensure any boards are firmly and properly located.
p.s. Please have a read of the forum rules, thanks.
