As far as the pricing goes... that's really going to depend on the scope of work that needs to be done AND your location. Your best bet is to have a shop take a look at it and have them quote you a price.
If i wanted to lower it a few inches while they are redoing the suspension would lowering spring be all i need?
Generally you'll want to change the struts and springs together if you want to lower the vehicle. If you plan on lowering it, do it the right way and get adjustable camber plates. These will save you a lot of $$ on tires.
In case you're not familiar with what I'm talking about here; when you lower a vehicle you change the suspension geometry and cause the top of the tires to lean inward. This will cause premature wear on the inside of the tires, thus decreasing the life of the tires by more than half. The adjustable camber plates will fix this negative camber angle.
also what all will i need to change in the
[FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif][FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]suspension[/font][/font] to make the front stop squeeking and make the back stop clanking?
Squeaking is usually caused by either; 1) A bad strut. 2) A worn spring seat. USUALLY.
The clanking in the back might be a bushing that's gone out in a sway bar or control arm. It could also be something not even related to the suspension (like a loose/missing exhaust hangar).
Hope this helps.