Hi First of all, though not an issue, try to migrate to another routing protocol XD
Legacy RIP is well legacy, be best you migrate to OSPF or EIGRP for future proofing.
In any case, SG300, typically is not that hard to understand.
If you look behind your SG300, it should have a serial RS232 console.
If you have the cable for it, then you can manage it through CLI.
If you do not have that kind of cable, then access the device through its UI, configure basic settings,
1. like the Mgmt VLAN and its IP and its gateway.
2. Enable Telnet and/or SSH for CLI access
-CLI is pretty much the same as IOS with a few exceptions esp. in the show commands, through it would be easy to understood, just use the all reliable '?' :P
For quick start guide, look at here: http://www.cisco.com/c/dam/en/us/td/docs/switches/lan/csbms/sf30x_sg30x/quick_start/78-19252-01.pdf
In my exp. we have deployed a few of these switches and we access through through its console port.
Configuration is pretty much the same with IOS CLI so it was easy to learn. Again, if you do not have the cable, then pre-configure the device through its GUI, once you have the mangaement done, telnet/ssh to it ^_^
