Not a difficult job, but always find a local garage with a friendly mechanic who can put the car up on a lift and show you the faulty part(s), and then discuss with you as to whether replacement parts should be sourced from the manufacturer or from the local motor factor. You can then look up the parts on line to see the range of prices that you may expect to pay.

The drop links for the Mk1 Focus are a tenner a pair on e-Bay and about a quarter of an hour lifting the car, changing them and dropping the car again.

If you can get the parts cheaper than the mechanic can get them from the local motor factor, then do so and just pay for the chap's labour to change them.

Drop links are a weak link ('scuse the pun) on many cars. Mahle do heavy duty versions for most vehicles. For my Saab they are £34 a pair on eBay.

I imagine you've been quoted the price for just doing one side. A minimum of 1 hours labour probably. Doing both sides together should only add a little time 'cos the car is already on the ramp and the tools are out.