I found that a small bottle jack (Harbor Freight $10-15) is very helpful in lining up the control arm. While the car is on your jack stands, put the bottle jack under the end of the control arm and raise it slowly while aligning it with wheel assembly.
--
1998 Volvo S70

Not a bad job. I replaced both control arms on my
850 - the ball joints failed and it is a one piece
deal (ball joint & control arm) I was also servicing
the wheel bearings at the time so it was not a big
deal to do the control arms - I would think you
should be able to replace the control arms without
having to mess with the axle. However, you would
want to be careful not to pull on the steering knuckle
assembly with the control arm off as it could cause
stress on the brake lines or axle joints.

Loosen the bolt that retains the ball joint to the
steering knuckle. Loosen and remove the control
arm bolts where they attach to the sub frame.
Pry the control arm out of the brackets on the
sub frame. Install your new control arms - the
bushings will be new and tight and you will have
to get the control arm aligned just right to fit into
the brackets on the sub frame - bolt it all back
up along with the ball joint to the knuckle and you
are done.

Here are some pictures of the wheel bearing replacement
on bay 13 - while you are not replacing the wheel bearing
it gives you some good views of the control arm you
will be dealing with.
http://www.volvospeed.com/Repair/FWDbearingHub.php

Have fun with it!
--
1990 240DL - 209K, 1989 Ranger 241K, Gone but not forgotten 1994 855