The Glenfield and Marlin Model 60's are the almost same rifle; trigger assemblies have changed slightly over the years. Very easy to field strip, you just need a screwdriver. Look it up on YouTube. Just don't disassemble the lower assembly once you have it field stripped (you'd have to take off some tiny e-clips to do that anyway); the lower is open & you can clean it without taking it apart.
I have a Marlin 60, Marlin 75, Glenfield 60, & an extra lower assembly. [did you know that the lower assemblies of the 75 & the 60 can be swapped on the barrelled receivers? Stock with the mag well is needed though for the 75 of course]
I got the Glenfield cheap also as a parts gun - it was REALLY dirty inside, and was missing mag tube inner assembly. Cleaned up with a new inner mag tube it runs flawlessly. If you start tinkering on these, you might get addicted.