I could be wrong, but it sounds to me like the OP already has some experience making/designing signs etc, just doesn't know the financial side of the business and the company already has advertising/design/large format printing experience. If they've been in business for 17 years I'd say they know at least something about being profitable.
I'd suggest you follow Jill/Jon/Checkers advice, invest in something like Estimate Software/Graphix Calc/Pricing Guide Book/etc. do some local market research and sit down with the powers that be at your company and figure out what you need to charge in order to be profitable and take it from there.
We use Estimate Software mostly and tweak as needed depending on the job.
I'd suggest you follow Jill/Jon/Checkers advice, invest in something like Estimate Software/Graphix Calc/Pricing Guide Book/etc. do some local market research and sit down with the powers that be at your company and figure out what you need to charge in order to be profitable and take it from there.
We use Estimate Software mostly and tweak as needed depending on the job.