Problem:
My home had 2 additions before I bought it without any electrical
upgrades. The addition in question is my bedroom (2nd floor) /garage
(ground level). It all runs into one 15A breaker in the main panel and
in the summer when I want to run my window AC unit and air compressor
(or other tool) at the same time, the breaker trips and cuts off all
power to both rooms.

Proposed solution:
I want to have a secondary breaker panel installed in the garage so I
can 1) seperate the garage & bedroom circuits, 2) run more wire for
more outlets, eliminating the need for extension cords all over the
floor and 3) have the option to create a couple 240v runs (or greater)
for larger tools if/when I acquire them.

The question:
What should this cost (ballpark figure)?

Further details:
- the garage is attached to the main part of the house
- the line from the electrical pole connects initially to the garage,
but runs to the meter mounted on the main part of the house.
- the current panel cannot be upgraded as it was walled in and moving
that wall involves moving plumbing as well. not something i want to
do.
- all i need is the breaker box installed and hooked into the meter. i
can do the rest.

Thanks-
Matt