RL70 is a Seatalk1 plotter. Depending on serial number of your existing radome, some of the C classic series chartplotters (C70, C120, etc) may be able to use it, but nothing else does. There's a lookup table for the serial numbers somewhere in the Raymarine knowledge base, if you want to go that route. So you'd be looking at replacing plotter + radome. The C classic series uses Compact flash charts instead of C-Map NT cards, so you'd have to replace your charts too.
Anything later is not compatible with Seatalk1. Your best bet is to replace plotter + radome with a current generation one and use a Seatalk1 to SeatalkNG (Raymarine's branding and connectors for NMEA2k) bridge. That way you can get your old (ST60 I presume) instruments connected to your new plotter.
Additionally, the vertical screen shape of the RL70 has fallen out of fashion, so most replacements mean having to rearrange your mounts (depending on how it is currently mounted, this may be easy or hard).