sheathing, windows and siding

[bushump]

Any suggestions, tips or just general help would be grateful.

I am getting ready to take down on all the old metal vertical siding. Going to re-insulate, add 1/2" sheathing, and frame in all new windows. Oh yeah a new metal roof as well. I have an older trailer with 2x3 studs in the walls. Should I fur those out to make them 2x4 thickness for insulation or just attach sheathing to 2x3 studs? What do you all think?

Thanks
Brandon

[Greg]

Well, you're in that deep might as well go for the extra insulation also.
A 2x6 ripped in half screwed to the face of the 2x3 would give you the depth of a 2x6 for half the cost.

Greg