I have been an RN for more than 20 yrs and this debate has not changed. Early in my career, we used lido subq on every IV start unless the pt had an allergy to it. After several yrs, someone decided lido is a med (duh!) and then required a physician's order. Many hospitals currently have a policy for prepping the IV site either with EMLA cream or lido subq. Check your facility's policy. I personally like to use it as it decreases anxiety/discomfort for patients but if administered too close to the vein may cause the it to "collapse" thus requiring another stick.
It's good to be a little nervous-makes you more aware and cautious. To answer your question, as with ANY central line, the patient may develop sepsis. As far as developing an infection after 1 episode of poor technique, it's a crap shoot!
As above, a PICC is a central line and should always be treated as such. They are designed for "short term" IV therapy for up to 12 weeks. Vacutainers are not recommended due to the amount of pressure created which can damage the internal catheter. I have been a nurse for 20 yrs, PICC certified for 10 yrs and my advise is proper sterile technique should be maintained as the tip is located in the tip of the superior vena cava.