There are several buses daily from Cajamarca that should not cost more than 10 soles, & twice weekly from Leimebamba. There are daily buses from Chachapoyas to Leimebamba. There are also combis (S/.10) that leave when they fill up and collectivos (S/.15).
Llanguat hot springs are about an hour from Celendin by car or three hours hiking. It has a semi-tropical climate so bug spray is necessary. Camping spots are available and you can ask the owner to make you dinner but there will not be many options--chicken or chicken.
Chachapoyas ruins can also be accessed from Celendin, then you can return by bus to chiclayo or continue on to Iquitos to get the full jungle tour.
"Local group to show you around": Celendín is certainly a nice place to stop. So far, it is well off the tourist trail, but there are some very nice places to visit, to walk to, great nature experiences to be had. If you want some local support, send Guido an email: email@example.com He and his group of environmentally dedicated friends (most are current or former students of environmental sciences) will be happy to organise a private tour to your liking. This is them: http://redeessperu.blogspot.com/