i was wondering if someone could help please?

i have recently bought a mk2 2.5 v6 ghiax mondeo which is an automatic the car has done 89943 miles and has stamps until 70+k so it has been cared for in the past and is pretty mint, the only problem is it has been left stood for a while.

in return of this since buying it, i hit a pot hole leaving a nice bubble in the tyre, then the original exhaust just decided to full off so had the whole thing replaced.

now the next problem is i was driving home from work the other night doing 70mph with the cruise control set, and i noticed the speedo start to dance like a butterfly which i thought were strange as it was decreasing but the car was not loosing speed.
then all of a sudden a lost the speedo altogether but was still cruising fine so i come off the motorway and get close to my house and thought i'd pull over stop the engine and restart after a minute or two.
the car started fine but i had noticed she was stuck into gear when put into drive she was revving at around 5k and not doing much speed at all.
i got to my house and put the car into reverse then drive and then in 2nd it seemed to change in ok, so i took her back out put the sport mode on with the overdrive and decided to boot it, the car then started to change gear but was kinda banging itself into gear rather than change smooth.
few days have passed and i drive around town in 2nd at the mo until she is going then will knock her up into drive, but when coming to a stop she will bang herself down the gear and sometimes cut out when stopped.

has anyone come accross this problem before or could tell me where to start or what to look for i'd be very gratefull as so far this motor is costing me an arm and a leg :0(

thanks