Mmmm......if the springs seemed to have lost their springiness, time to replace. You could just de-gunk it with a good degreaser and small brush, let it dry, oil with a very light machine oil and then see if it feels significantly better? If it does, great. If not, it'll be strip down time. I've not ever had to do one personally, but it looks easy enough. As you've said, there will be plenty of on-line tutorials (the Shooting at dawn one seems very good).

Protek have spares in for the trigger units, methinks.

Getting the little spring for the single sided safety catch might be tricky - I think some have managed to get away with using biro springs in the past?

Did there seem to be sufficient clearance between wood and trigger?