I think your tele job sounds like a great opportunity, but agree that 4 weeks is painfully short for a new grad orientation. Before you start, get yourself in the mind set of a hospital nurse. Review all your cardiac stuff from nursing school. Make sure you're up to date on common medications (beta blockers, calcium channel blockers, diuretics, ace inhibitors, etc.). I'm sure you knew them all at one point, so just brush up on the "-lols" vs the "-prils" and so forth. There are lots of resources online to practice rhythm interpretation, so do some exercises since you will undoubtably be expected to read the telly strips and EKGs.
If it's been a while since you took a manual blood pressure, get out your cuff and your stethoscope from nursing school and practice on family members and friends. Heck, see if you can talk them into listening to their lungs and finding their pedal pulses. On telemetry, you'll come across a lot of people with lower extremity edema, and sometimes it can be tough to palpate their pulses. Don't be afraid to ask your preceptor for his/her tips on assessments for acute cardiac patients, and realize that even seasoned RNs sometimes have to get a doppler.
Of course, your cardiac patients will also just be regular med-surg patients, so check out YouTube for videos of common procedures. Since you haven't placed a foley in a year, review those steps. Little things like that can help you feel better prepared when you come across them at the hospital because the visual will be fresh in your mind.
Also realize that you're not expected to know everything or have done everything. We weren't allowed to start IVs when I was in nursing school, and I got very little training in that when I was going through orientation, so I frequently ask someone else to start one for me if a patient has tricky veins. To be honest, lots of experienced floor nurses kind of suck at IVs.
Lastly, be honest with your preceptor. Tell him or her that you're a bit out of practice with some of the hands-on nursing you learned in nursing school, and maybe talk through the steps before you go into a patient's room to perform certain tasks. For me, the biggest change between student nursing and floor nursing was the organization and prioritization necessary to take care of 5 or 6 patients rather than 1 or 2. I remember asking for feedback and advice on this because it was clearly my weak spot. One nurse told me, "You're already a safe nurse. Now you need to become an efficient nurse." You don't have much time with your preceptor, so be really proactive about asking for help and be diligent about putting it to practice.
Now breathe. You CAN do this!