Definitely. Use shells whenever possible for thin-walled parts or at least hex/wedge elements. Meshing with the latter has some requirements since they can be created only via revolution, extrusion, sweep or using the transfinite Gmsh algorithm that needs subvolumes with 5/6 faces (having 3/4 edges each). Alternatively, you can use the Thicken Shell Mesh tool. So try extracting midsurfaces from these long thin-walled parts in your CAD software and meshing them with shells first. If you encounter any CalculiX issues with 2D elements, you can always thicken them and use solids.
Apart from that, if you want to get your analysis to run, even just to see what happens in it (maybe there’s some modeling mistake), make it linear (replace contacts with tie constraints), run a frequency step to check the connections and then a linear static step to see if the results make any physical sense. Still, you will need to fix the mesh to get reasonably accurate results.
And if you get errors such as “zero coefficient on the dependent side of an equation” then there might be some overconstraint in your model, likely with tie constraints. Check and correct them as explained here: [Solved] Why does increasing the size of parts lead to an error? - #2 by FEAnalyst