Big problem with Speedo needle calibration?

[91dsmtalon]

Already searched through the forums and saw quite a bit of information about how screwed you are if you mess with your needles on your gauge cluster. Oops...was trying to pull it out to figure out why the hell my Oil pressure gauge dosent work and ended up bumping my speedometer needle. I on the other hand bumped the needle down, Im guessing what the speedometer tells me is a good 10mph slower than what I am going. So,
1) Can I fix that by matching speed and trying to put the needle back on at the aprox speed?
2) If I were to buy a new Gauge cluster and I bought one w/out a boostgauge (I am a 91 Tsi Awd) would it all be accurate just without boost gauge?

 

[mdctalon]

When I changed my guages, i had the problem, it was constantly off by 15mph, My friend suggested I push the spedo needle as far as I could until you hear a clicking noise, it took a couple tries, and it was at the point where the needle was past 140mph. but it worked for me.

 

[jessebenner]

I had to take my needle off when I put my new gauge faces on. The first time, I just got my dad to drive his car out with me and I followed him, and when he signaled out the window (which meant he was doing exactly 40mph) I pushed the needle back on at 40. It took a couple tries, but I finally got it.

The second time, I knew not to take the needle off until I was ready. So going down the highway, I set my cruise at 60, removed the needle, did my business, and put everything back together with the needle still at 60.