El cheapo Series gearbox

I just picked up a "good running" series II box for next to nothing, and
upon opening the crate I discovered that it had been partialy dissassembled
to fit in said crate.

Since it was already in bits, I had a bit of a look around, the bearings
look and feel like new, and all the gears look real good except first gear
on the layshaft (small straight cut) which appears quite pitted :-(

I take it this is the first to show wear, will I get away with just
replacing first gear?

Cheers.

Steve.