I would recommend taking booth end caps off to get at best at everything, but taking the mast end (tack end) off will always work, though taking the clew end can sometimes work depending on your purchase setup.
If you are taking the tack end boom cap off.... the process involves cutting the outhaul wire at the schackle/swage so that it will be able to go through the pulley at the clew end. Then tape a messenger line on that is the length of the boom plus a couple of feet. Tie the free end of the messenger line to the clew end of the boom (around the boom works). You likely want to tape a messenger line to the rope end of the outhaul, too. Then when you remove the tack end cap of the boom you can pull all the internals out.
This is one version of what your outhaul may look like - it is for a cascading 6x1 purchase, drawing courtesy of the Shark fleet.

As you can see, for the purchases to work, one end needs to be fixed. The first 2x1 attaches at "A" at the mast end of the boom. Then the second 3x1 attaches separately at B, also at the mast end (the 2x3 gives you a 6x1). This cascades will more freely and take of less space than a single 6x1 purchase.
You may have something more simple than the above, a single 3x1 or 4x1.

is a 4x1. Note that if you don't have a line terminating on the mast end cap (either directly or on a becket block that is attached to the mast end cap) you can get all the internals out from the aft end of the boom. You just need an extra long messenger line on the line end of the outhaul ( 3 or 4 times the length of the boom depending on the amount of purchase).
If you Google "internal outhaul" there is a fair amount of info on the net.
Erik & Evi
F40CC Raven