Assuming you end up in Calais, go out of the port on the dual c'way for about 2 miles and turn left onto the 'corridor' motorway towards Brussels. If you come via the Eurotunnel you will simply turn right out of the terminal on to this motorway. There is no need to turn off this road, you can just follow it all the way to the Brussels ring road. Turn left onto the ring road (towards the airport). You have to go on the ring road for about 10 mins and take the E42 turn (I think. I can check). Follow this road for about 5 miles then take the E40 or E42 (I'll have to check again!) to Aachen. Cross into Germany (becomes the A4)[A=autobahn=motorway]. Follow for about 45 miles to Koln and turn right(south) onto the A61. Just south of Koblenz, turn left (east) onto the A60 into Frankfurt. When I used to drive my truck over there, I was limited to 56mph and get to Koln in 4 hours and do Frankfurt in about 6 1/2, so you should easily do it in 5 1/2 hours in a car.
Crossing the channel, you basically have the choice of boat or tunnel. Tunnel is very quick(30 mins crossing) but can be pricey if you pick the wrong time. Dover - Calais ferries are either P&O Stena or SeaFrance. P&O cross about every hour or 2, but SeaFrance every 2 or 3 hours. Due to the frequency P&O is usually more expensive. I'm afraid you will have to see what deals you can get. Ferry crossing is about 1 1/2 hours. If you need to know more, post here again and I'll look up the road numbers etc.