for the screen i would say around £60-70
for the jack, assuming its on the inside, you can replace it for around £2-3
bear in mind that the jack may need soldering
the screen shouldnt be too hard, take the case off until you get to the screen connector, once you get there take the lid off and work on the lid, overall i wouldnt say it is too hard
the jack will be harder, you will need to get the motherboard out and disconnect any batteries, wires etc.
then you will need to de-solder the old jack and make sure the holes are clear (de-soldering takes more heat than soldering so be careful not to burn or break any of the surrounding components, or your hand ;)).
once the holes are clear you should be able to just put the jack on and solder
if your lucky you may have one like my dads where the jack plugs in to the board and you will just need to glue the lack down
just a idea on the cost
screen:
http://cgi.ebay.co.uk/New-Acer-Aspire-AS5742Z-4685-15-6-HD-LED-Glossy-Screen-/230561884664?pt=UK_Computing_LaptopAccess_RL&hash=item35ae8f29f8#ht_1118wt_905 or
http://cgi.ebay.co.uk/FUJITSU-LIFEBOOK-CP126178-15-XGA-LCD-SCREEN-MATT-/270437325920?pt=UK_Computing_LaptopAccess_RL&hash=item3ef7521c60#ht_747wt_905Plug-in jack:
http://cgi.ebay.co.uk/IBM-THINKPAD-T41-JACK-POWER-PIN-/270613698497?pt=UK_Computing_LaptopAccess_RL&hash=item3f01d557c1#ht_901wt_905Jack:
http://cgi.ebay.co.uk/DC-Power-Jack-Socket-PJ03-2-5-Advent-7104-Brand-New-/220632729896?pt=UK_Computing_LaptopAccessories_PowerSupplies&hash=item335ebc4928so overall price, no more than £70
~shut