You need to have your cooling system flushed with a mild acid, get it filled with a 50:50 mixture of good quality coolant and distilled water, install a thermostat valve, and get your fan to run automatically.
Depending on the level of damage (rust, corrosion, and leaks) in the cooling circuit, you might need to get some parts replaced as well.
It's an easy enough DIY job; there are detailed threads about it on these forums. Any mechanic who isn't braindead can do this job as well.
Khyber's engine has a problem with corroded freeze plugs (tikkian in desi language), when run on plain water for too long - just pray that your engine doesn't have it, otherwise the head needs to be opened (my car needed this job).
Its all well worth it in the end - you'll have a fuel efficient engine that lasts ages without problems.