Any piston scoring is bad, and the future for your
trimmer is bleak. Hate to say it, but your money would
be best spent buying a new one. If you buy the same
model, at least you will have one for parts. If you want
a different brand, look at Shindaiwa or Echo. Putting
in a new piston and/or cylinder would approach the
cost of a new one, and then still you would need to
find out what damaged the piston to begin with.