These cars are very reliable and have a nice ride which can be adjusted from firm to plush based on your preference. If you keep up with basic maintenance you shouldn't have any big Issues other then the airbag suspension. If it craps out it could be expensive such as on the Mark 8. I have a 97 with 160k+ miles on it and to date it hasn't had any major issues other then the transmission and that was in August of 97. As far as mods go You should consider the Grille and Emblem from the 97 it makes the front of the car look better in my opinion. Also H.I.Ds, Rims, Chrome Pillars, Exhaust, Removing Air Silencer. Those are just a few of the mods you can do. Remember it has the same engine as the Mark so most of the performance things from the Mark will work on the Conti afaik.
I hope that's helped a bit
. 98-02 Contis have the same engine and general layout but are very different physically. I have a very heavy foot and am currently getting about 18-19 in town but On the highway I've managed to go SC to MD on a take of gas. Mileage on these cars is good and ofcourse the V8 is extra nice Try asking your friend if you can ride with him and give it a test drive around the neighborhood.
me and him were back to back i had my mark and he had the conti and we both punched it he skirted and i sat there and didnt realize that i was leaving 2 marks on the road from his house to mine that have been there since thanksgiving!!! we also raced and it wasnt to far off from (behind) my mark
you get the point.