Welcome ! The 748 is a fantastic bike. and would make an excellent 1st bike. Its fast, it has some balls, its not hard to ride, and being a first time rider it will serve you well. Its not "too much" of a bike. My sister has an 02 748s that is kept at my house, and that bike just flat out hauls, i love it! Its hard to imagine how my 1098 is gonna feel to the 748. Look in My registry to see a pic of it.
Before you by any used Ducati, make sure it has all the maintenance records since day one! Ducati's require frequent maintenance in order to keep them running well. Mainly valve adj and belt replacements. this is done every 7500 mi. labor on the full maintenance varies from dealer, but generally is around $ 500-700. If the bike did not have servicing done regularly it can be disastrous. - stay away from these. Parts maintenance and labor for these bikes are expensive, so make sure you know what your getting into before you buy. If the above didn't scare you off, great welcome to the world of Ducati! There is no other bikes like it on the road!
IMO i would also stay away from bikes that have been heavily modified.
If possible i would have a dealer give the bike a good look over.
Have the rockers checked out, there was a problem with some of them, with the plating chipping off. That's something that ducati should still take care of even though its out of warranty.
Typical mods for ducs are exhausts, open clutch covers, pressure plates, re gearing, and replacing the clutch slave cylinder. You may also want to consider and side stand "cheater" harness, that will allow you to start the bike in Neutral while the side stand is down. From the factory the bike will not start unless if your on the bike with the side stand up. Its a pain in the ass while your letting it warm up, Its an easy mod and costs around $30.
When you find the right Ducati, it will treat you well, and you will have a blast. The grin on your face will stay, long after your off the bike!