I had a 1999 S-Type and it was an excellent car. It was the 3.0 petrol and did about late 20's solo and low 20's towing. It towed a 1300Kg van with ease and was a joy to drive and own (240bhp).
I replaced one of the front suspension bushes, had a set of new coils and a door lock - these were all common failures on early S-Types. After about 2001 I think they had a facelift and put right some of the common problems.
I got mine serviced at an Indy and it cost no more than most other large cars. It was the most comfortable car I have been in and when I changed it for a BMW 5 series all my family prefered the Jag!
They can be picked up quite cheaply nowerdays and I think they are an absolute bargain, I would recommend them to anyone.
Graeme.