After all these years my antenna sheared off at the mounting. Honda wants $300 parts and labor to replace the antenna. Thought I might be able to tackle the job myself as I used to fix/install/remove 2-way radios. But, I'm not sure how extensive it is to snake the cable under the dash, if it must come out, what part, and if it's even worth it for a car this age (168,000 miles) and the sterio is shot to make things more interesting and needs replacement itself. Is this do-able?

Any step by step instructions would be appreciated.
Thanks,
Dave G. (Sharon, MA)