I'm new to the world of ham radio so this might be obvoius, but I have a Baofeng UV-82 which can transmit and receive up to 520MHz. I need to be able to transmit and receive on frequencies up to 1GHz. Is there anything I can buy or build to achieve this?
Yes. You're looking for a transverter that will take RF from one source (your radio) and treat it as if it were an IF stage into another system. Here is an example.
Obviously, you'll need to take care that you have operating privileges at the output of the transverter, including making sure spurious emissions are appropriately suppressed, etc.
You won't be able to, basically you'd have to redesign the whole radio. For example even if you somehow increased the frequency, there would be filters that follow that would cut down the signal. Everything is tuned and matched for a certain frequency range. There are other options but not for the Baofeng.
Welcome to ham radio!
Sorry, but there isn't anything practical that you could do to make your Baofeng UV-82 transmit at substantially-higher frequencies.
The obvious answer is of course to buy a radio for the frequency band that you'd like to use. In the US there is a 33 cm ham band from 902 – 928 MHz, and commercial-band radios use similar frequencies.
You could also make your own equipment. You could use a Software-Defined Radio (SDR) device such as a HackRF One (many such devices exist; I picked that particular one more-or-less at random from a list of questions here about SDR), plus software on your computer such as GNURadio, to build a receiver for an arbitrary frequency. 1 GHz is not difficult these days.
Transmitting is more complicated. You could make an SDR transmitter in a similar way as an SDR receiver, but there are legal requirements to comply with. You must be familiar with the relevant laws. In the US, one can transmit in the various Industrial, Scientific, and Medical (ISM) bands without a license, but only at low power. Licensed hams can transmit with more power in the ham bands, but there are rules about spectral purity that would require passing the transmitted signal through a filter designed for the band to limit harmonics. There are also laws about modulation methods, bandwidth, content, etc. that must be observed.
Beyond the ISM and ham bands, one is limited to using type-accepted radios in most jurisdictions, which means that the only legal alternative is to buy a commercially-made radio. Licenses are typically required also.